1650 lines
54 KiB
Plaintext
1650 lines
54 KiB
Plaintext
@node Error Reporting, Memory, Introduction, Top
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@chapter Error Reporting
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@c %MENU% How library functions report errors
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@cindex error reporting
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@cindex reporting errors
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@cindex error codes
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@cindex status codes
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Many functions in the GNU C library detect and report error conditions,
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and sometimes your programs need to check for these error conditions.
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For example, when you open an input file, you should verify that the
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file was actually opened correctly, and print an error message or take
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other appropriate action if the call to the library function failed.
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This chapter describes how the error reporting facility works. Your
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program should include the header file @file{errno.h} to use this
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facility.
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@pindex errno.h
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@menu
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* Checking for Errors:: How errors are reported by library functions.
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* Error Codes:: Error code macros; all of these expand
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into integer constant values.
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* Error Messages:: Mapping error codes onto error messages.
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@end menu
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@node Checking for Errors, Error Codes, , Error Reporting
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@section Checking for Errors
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Most library functions return a special value to indicate that they have
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failed. The special value is typically @code{-1}, a null pointer, or a
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constant such as @code{EOF} that is defined for that purpose. But this
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return value tells you only that an error has occurred. To find out
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what kind of error it was, you need to look at the error code stored in the
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variable @code{errno}. This variable is declared in the header file
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@file{errno.h}.
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@pindex errno.h
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@comment errno.h
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@comment ISO
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@deftypevr {Variable} {volatile int} errno
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The variable @code{errno} contains the system error number. You can
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change the value of @code{errno}.
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Since @code{errno} is declared @code{volatile}, it might be changed
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asynchronously by a signal handler; see @ref{Defining Handlers}.
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However, a properly written signal handler saves and restores the value
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of @code{errno}, so you generally do not need to worry about this
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possibility except when writing signal handlers.
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The initial value of @code{errno} at program startup is zero. Many
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library functions are guaranteed to set it to certain nonzero values
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when they encounter certain kinds of errors. These error conditions are
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listed for each function. These functions do not change @code{errno}
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when they succeed; thus, the value of @code{errno} after a successful
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call is not necessarily zero, and you should not use @code{errno} to
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determine @emph{whether} a call failed. The proper way to do that is
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documented for each function. @emph{If} the call failed, you can
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examine @code{errno}.
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Many library functions can set @code{errno} to a nonzero value as a
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result of calling other library functions which might fail. You should
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assume that any library function might alter @code{errno} when the
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function returns an error.
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@strong{Portability Note:} @w{ISO C} specifies @code{errno} as a
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``modifiable lvalue'' rather than as a variable, permitting it to be
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implemented as a macro. For example, its expansion might involve a
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function call, like @w{@code{*_errno ()}}. In fact, that is what it is
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on the GNU system itself. The GNU library, on non-GNU systems, does
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whatever is right for the particular system.
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There are a few library functions, like @code{sqrt} and @code{atan},
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that return a perfectly legitimate value in case of an error, but also
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set @code{errno}. For these functions, if you want to check to see
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whether an error occurred, the recommended method is to set @code{errno}
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to zero before calling the function, and then check its value afterward.
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@end deftypevr
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@pindex errno.h
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All the error codes have symbolic names; they are macros defined in
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@file{errno.h}. The names start with @samp{E} and an upper-case
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letter or digit; you should consider names of this form to be
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reserved names. @xref{Reserved Names}.
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The error code values are all positive integers and are all distinct,
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with one exception: @code{EWOULDBLOCK} and @code{EAGAIN} are the same.
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Since the values are distinct, you can use them as labels in a
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@code{switch} statement; just don't use both @code{EWOULDBLOCK} and
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@code{EAGAIN}. Your program should not make any other assumptions about
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the specific values of these symbolic constants.
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The value of @code{errno} doesn't necessarily have to correspond to any
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of these macros, since some library functions might return other error
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codes of their own for other situations. The only values that are
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guaranteed to be meaningful for a particular library function are the
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ones that this manual lists for that function.
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On non-GNU systems, almost any system call can return @code{EFAULT} if
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it is given an invalid pointer as an argument. Since this could only
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happen as a result of a bug in your program, and since it will not
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happen on the GNU system, we have saved space by not mentioning
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@code{EFAULT} in the descriptions of individual functions.
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In some Unix systems, many system calls can also return @code{EFAULT} if
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given as an argument a pointer into the stack, and the kernel for some
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obscure reason fails in its attempt to extend the stack. If this ever
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happens, you should probably try using statically or dynamically
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allocated memory instead of stack memory on that system.
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@node Error Codes, Error Messages, Checking for Errors, Error Reporting
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@section Error Codes
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@pindex errno.h
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The error code macros are defined in the header file @file{errno.h}.
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All of them expand into integer constant values. Some of these error
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codes can't occur on the GNU system, but they can occur using the GNU
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library on other systems.
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@comment errno.h
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@comment POSIX.1: Operation not permitted
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@deftypevr Macro int EPERM
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@comment errno 1 @c DO NOT REMOVE
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Operation not permitted; only the owner of the file (or other resource)
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or processes with special privileges can perform the operation.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: No such file or directory
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@deftypevr Macro int ENOENT
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@comment errno 2 @c DO NOT REMOVE
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No such file or directory. This is a ``file doesn't exist'' error
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for ordinary files that are referenced in contexts where they are
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expected to already exist.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: No such process
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@deftypevr Macro int ESRCH
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@comment errno 3 @c DO NOT REMOVE
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No process matches the specified process ID.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Interrupted system call
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@deftypevr Macro int EINTR
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@comment errno 4 @c DO NOT REMOVE
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Interrupted function call; an asynchronous signal occurred and prevented
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completion of the call. When this happens, you should try the call
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again.
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You can choose to have functions resume after a signal that is handled,
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rather than failing with @code{EINTR}; see @ref{Interrupted
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Primitives}.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Input/output error
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@deftypevr Macro int EIO
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@comment errno 5 @c DO NOT REMOVE
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Input/output error; usually used for physical read or write errors.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: No such device or address
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@deftypevr Macro int ENXIO
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@comment errno 6 @c DO NOT REMOVE
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No such device or address. The system tried to use the device
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represented by a file you specified, and it couldn't find the device.
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This can mean that the device file was installed incorrectly, or that
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the physical device is missing or not correctly attached to the
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computer.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Argument list too long
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@deftypevr Macro int E2BIG
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@comment errno 7 @c DO NOT REMOVE
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Argument list too long; used when the arguments passed to a new program
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being executed with one of the @code{exec} functions (@pxref{Executing a
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File}) occupy too much memory space. This condition never arises in the
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GNU system.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Exec format error
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@deftypevr Macro int ENOEXEC
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@comment errno 8 @c DO NOT REMOVE
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Invalid executable file format. This condition is detected by the
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@code{exec} functions; see @ref{Executing a File}.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Bad file descriptor
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@deftypevr Macro int EBADF
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@comment errno 9 @c DO NOT REMOVE
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Bad file descriptor; for example, I/O on a descriptor that has been
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closed or reading from a descriptor open only for writing (or vice
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versa).
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: No child processes
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@deftypevr Macro int ECHILD
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@comment errno 10 @c DO NOT REMOVE
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There are no child processes. This error happens on operations that are
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supposed to manipulate child processes, when there aren't any processes
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to manipulate.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Resource deadlock avoided
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@deftypevr Macro int EDEADLK
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@comment errno 11 @c DO NOT REMOVE
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Deadlock avoided; allocating a system resource would have resulted in a
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deadlock situation. The system does not guarantee that it will notice
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all such situations. This error means you got lucky and the system
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noticed; it might just hang. @xref{File Locks}, for an example.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Cannot allocate memory
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@deftypevr Macro int ENOMEM
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@comment errno 12 @c DO NOT REMOVE
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No memory available. The system cannot allocate more virtual memory
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because its capacity is full.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Permission denied
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@deftypevr Macro int EACCES
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@comment errno 13 @c DO NOT REMOVE
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Permission denied; the file permissions do not allow the attempted operation.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Bad address
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@deftypevr Macro int EFAULT
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@comment errno 14 @c DO NOT REMOVE
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Bad address; an invalid pointer was detected.
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In the GNU system, this error never happens; you get a signal instead.
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@end deftypevr
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@comment errno.h
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@comment BSD: Block device required
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@deftypevr Macro int ENOTBLK
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@comment errno 15 @c DO NOT REMOVE
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A file that isn't a block special file was given in a situation that
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requires one. For example, trying to mount an ordinary file as a file
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system in Unix gives this error.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Device or resource busy
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@deftypevr Macro int EBUSY
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@comment errno 16 @c DO NOT REMOVE
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Resource busy; a system resource that can't be shared is already in use.
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For example, if you try to delete a file that is the root of a currently
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mounted filesystem, you get this error.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: File exists
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@deftypevr Macro int EEXIST
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@comment errno 17 @c DO NOT REMOVE
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File exists; an existing file was specified in a context where it only
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makes sense to specify a new file.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Invalid cross-device link
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@deftypevr Macro int EXDEV
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@comment errno 18 @c DO NOT REMOVE
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An attempt to make an improper link across file systems was detected.
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This happens not only when you use @code{link} (@pxref{Hard Links}) but
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also when you rename a file with @code{rename} (@pxref{Renaming Files}).
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: No such device
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@deftypevr Macro int ENODEV
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@comment errno 19 @c DO NOT REMOVE
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The wrong type of device was given to a function that expects a
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particular sort of device.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Not a directory
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@deftypevr Macro int ENOTDIR
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@comment errno 20 @c DO NOT REMOVE
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A file that isn't a directory was specified when a directory is required.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Is a directory
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@deftypevr Macro int EISDIR
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@comment errno 21 @c DO NOT REMOVE
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File is a directory; you cannot open a directory for writing,
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or create or remove hard links to it.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Invalid argument
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@deftypevr Macro int EINVAL
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@comment errno 22 @c DO NOT REMOVE
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Invalid argument. This is used to indicate various kinds of problems
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with passing the wrong argument to a library function.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Too many open files
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@deftypevr Macro int EMFILE
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@comment errno 24 @c DO NOT REMOVE
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The current process has too many files open and can't open any more.
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Duplicate descriptors do count toward this limit.
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In BSD and GNU, the number of open files is controlled by a resource
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limit that can usually be increased. If you get this error, you might
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want to increase the @code{RLIMIT_NOFILE} limit or make it unlimited;
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@pxref{Limits on Resources}.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Too many open files in system
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@deftypevr Macro int ENFILE
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@comment errno 23 @c DO NOT REMOVE
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There are too many distinct file openings in the entire system. Note
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that any number of linked channels count as just one file opening; see
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@ref{Linked Channels}. This error never occurs in the GNU system.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Inappropriate ioctl for device
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@deftypevr Macro int ENOTTY
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@comment errno 25 @c DO NOT REMOVE
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Inappropriate I/O control operation, such as trying to set terminal
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modes on an ordinary file.
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@end deftypevr
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@comment errno.h
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@comment BSD: Text file busy
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@deftypevr Macro int ETXTBSY
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@comment errno 26 @c DO NOT REMOVE
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An attempt to execute a file that is currently open for writing, or
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write to a file that is currently being executed. Often using a
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debugger to run a program is considered having it open for writing and
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will cause this error. (The name stands for ``text file busy''.) This
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is not an error in the GNU system; the text is copied as necessary.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: File too large
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@deftypevr Macro int EFBIG
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@comment errno 27 @c DO NOT REMOVE
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File too big; the size of a file would be larger than allowed by the system.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: No space left on device
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@deftypevr Macro int ENOSPC
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@comment errno 28 @c DO NOT REMOVE
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No space left on device; write operation on a file failed because the
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disk is full.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Illegal seek
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@deftypevr Macro int ESPIPE
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@comment errno 29 @c DO NOT REMOVE
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Invalid seek operation (such as on a pipe).
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Read-only file system
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@deftypevr Macro int EROFS
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@comment errno 30 @c DO NOT REMOVE
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An attempt was made to modify something on a read-only file system.
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Too many links
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@deftypevr Macro int EMLINK
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@comment errno 31 @c DO NOT REMOVE
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Too many links; the link count of a single file would become too large.
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@code{rename} can cause this error if the file being renamed already has
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as many links as it can take (@pxref{Renaming Files}).
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@end deftypevr
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@comment errno.h
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@comment POSIX.1: Broken pipe
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@deftypevr Macro int EPIPE
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@comment errno 32 @c DO NOT REMOVE
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Broken pipe; there is no process reading from the other end of a pipe.
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Every library function that returns this error code also generates a
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@code{SIGPIPE} signal; this signal terminates the program if not handled
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or blocked. Thus, your program will never actually see @code{EPIPE}
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unless it has handled or blocked @code{SIGPIPE}.
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@end deftypevr
|
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|
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@comment errno.h
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|
@comment ISO: Numerical argument out of domain
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|
@deftypevr Macro int EDOM
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@comment errno 33 @c DO NOT REMOVE
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Domain error; used by mathematical functions when an argument value does
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not fall into the domain over which the function is defined.
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@end deftypevr
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|
|
@comment errno.h
|
|
@comment ISO: Numerical result out of range
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|
@deftypevr Macro int ERANGE
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@comment errno 34 @c DO NOT REMOVE
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Range error; used by mathematical functions when the result value is
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not representable because of overflow or underflow.
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@end deftypevr
|
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|
|
@comment errno.h
|
|
@comment POSIX.1: Resource temporarily unavailable
|
|
@deftypevr Macro int EAGAIN
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@comment errno 35 @c DO NOT REMOVE
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Resource temporarily unavailable; the call might work if you try again
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later. The macro @code{EWOULDBLOCK} is another name for @code{EAGAIN};
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they are always the same in the GNU C library.
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This error can happen in a few different situations:
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@itemize @bullet
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@item
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An operation that would block was attempted on an object that has
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non-blocking mode selected. Trying the same operation again will block
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|
until some external condition makes it possible to read, write, or
|
|
connect (whatever the operation). You can use @code{select} to find out
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|
when the operation will be possible; @pxref{Waiting for I/O}.
|
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|
@strong{Portability Note:} In many older Unix systems, this condition
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was indicated by @code{EWOULDBLOCK}, which was a distinct error code
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different from @code{EAGAIN}. To make your program portable, you should
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|
check for both codes and treat them the same.
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|
@item
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A temporary resource shortage made an operation impossible. @code{fork}
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can return this error. It indicates that the shortage is expected to
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pass, so your program can try the call again later and it may succeed.
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|
It is probably a good idea to delay for a few seconds before trying it
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|
again, to allow time for other processes to release scarce resources.
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|
Such shortages are usually fairly serious and affect the whole system,
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|
so usually an interactive program should report the error to the user
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and return to its command loop.
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@end itemize
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@end deftypevr
|
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|
|
@comment errno.h
|
|
@comment BSD: Operation would block
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@deftypevr Macro int EWOULDBLOCK
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|
@comment errno EAGAIN @c DO NOT REMOVE
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In the GNU C library, this is another name for @code{EAGAIN} (above).
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The values are always the same, on every operating system.
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|
|
C libraries in many older Unix systems have @code{EWOULDBLOCK} as a
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separate error code.
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|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Operation now in progress
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@deftypevr Macro int EINPROGRESS
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@comment errno 36 @c DO NOT REMOVE
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|
An operation that cannot complete immediately was initiated on an object
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that has non-blocking mode selected. Some functions that must always
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|
block (such as @code{connect}; @pxref{Connecting}) never return
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@code{EAGAIN}. Instead, they return @code{EINPROGRESS} to indicate that
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the operation has begun and will take some time. Attempts to manipulate
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the object before the call completes return @code{EALREADY}. You can
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|
use the @code{select} function to find out when the pending operation
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|
has completed; @pxref{Waiting for I/O}.
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@end deftypevr
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|
|
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@comment errno.h
|
|
@comment BSD: Operation already in progress
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@deftypevr Macro int EALREADY
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@comment errno 37 @c DO NOT REMOVE
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|
An operation is already in progress on an object that has non-blocking
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mode selected.
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@end deftypevr
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|
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@comment errno.h
|
|
@comment BSD: Socket operation on non-socket
|
|
@deftypevr Macro int ENOTSOCK
|
|
@comment errno 38 @c DO NOT REMOVE
|
|
A file that isn't a socket was specified when a socket is required.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Message too long
|
|
@deftypevr Macro int EMSGSIZE
|
|
@comment errno 40 @c DO NOT REMOVE
|
|
The size of a message sent on a socket was larger than the supported
|
|
maximum size.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Protocol wrong type for socket
|
|
@deftypevr Macro int EPROTOTYPE
|
|
@comment errno 41 @c DO NOT REMOVE
|
|
The socket type does not support the requested communications protocol.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Protocol not available
|
|
@deftypevr Macro int ENOPROTOOPT
|
|
@comment errno 42 @c DO NOT REMOVE
|
|
You specified a socket option that doesn't make sense for the
|
|
particular protocol being used by the socket. @xref{Socket Options}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Protocol not supported
|
|
@deftypevr Macro int EPROTONOSUPPORT
|
|
@comment errno 43 @c DO NOT REMOVE
|
|
The socket domain does not support the requested communications protocol
|
|
(perhaps because the requested protocol is completely invalid).
|
|
@xref{Creating a Socket}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Socket type not supported
|
|
@deftypevr Macro int ESOCKTNOSUPPORT
|
|
@comment errno 44 @c DO NOT REMOVE
|
|
The socket type is not supported.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Operation not supported
|
|
@deftypevr Macro int EOPNOTSUPP
|
|
@comment errno 45 @c DO NOT REMOVE
|
|
The operation you requested is not supported. Some socket functions
|
|
don't make sense for all types of sockets, and others may not be
|
|
implemented for all communications protocols. In the GNU system, this
|
|
error can happen for many calls when the object does not support the
|
|
particular operation; it is a generic indication that the server knows
|
|
nothing to do for that call.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Protocol family not supported
|
|
@deftypevr Macro int EPFNOSUPPORT
|
|
@comment errno 46 @c DO NOT REMOVE
|
|
The socket communications protocol family you requested is not supported.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Address family not supported by protocol
|
|
@deftypevr Macro int EAFNOSUPPORT
|
|
@comment errno 47 @c DO NOT REMOVE
|
|
The address family specified for a socket is not supported; it is
|
|
inconsistent with the protocol being used on the socket. @xref{Sockets}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Address already in use
|
|
@deftypevr Macro int EADDRINUSE
|
|
@comment errno 48 @c DO NOT REMOVE
|
|
The requested socket address is already in use. @xref{Socket Addresses}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Cannot assign requested address
|
|
@deftypevr Macro int EADDRNOTAVAIL
|
|
@comment errno 49 @c DO NOT REMOVE
|
|
The requested socket address is not available; for example, you tried
|
|
to give a socket a name that doesn't match the local host name.
|
|
@xref{Socket Addresses}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Network is down
|
|
@deftypevr Macro int ENETDOWN
|
|
@comment errno 50 @c DO NOT REMOVE
|
|
A socket operation failed because the network was down.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Network is unreachable
|
|
@deftypevr Macro int ENETUNREACH
|
|
@comment errno 51 @c DO NOT REMOVE
|
|
A socket operation failed because the subnet containing the remote host
|
|
was unreachable.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Network dropped connection on reset
|
|
@deftypevr Macro int ENETRESET
|
|
@comment errno 52 @c DO NOT REMOVE
|
|
A network connection was reset because the remote host crashed.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Software caused connection abort
|
|
@deftypevr Macro int ECONNABORTED
|
|
@comment errno 53 @c DO NOT REMOVE
|
|
A network connection was aborted locally.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Connection reset by peer
|
|
@deftypevr Macro int ECONNRESET
|
|
@comment errno 54 @c DO NOT REMOVE
|
|
A network connection was closed for reasons outside the control of the
|
|
local host, such as by the remote machine rebooting or an unrecoverable
|
|
protocol violation.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: No buffer space available
|
|
@deftypevr Macro int ENOBUFS
|
|
@comment errno 55 @c DO NOT REMOVE
|
|
The kernel's buffers for I/O operations are all in use. In GNU, this
|
|
error is always synonymous with @code{ENOMEM}; you may get one or the
|
|
other from network operations.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Transport endpoint is already connected
|
|
@deftypevr Macro int EISCONN
|
|
@comment errno 56 @c DO NOT REMOVE
|
|
You tried to connect a socket that is already connected.
|
|
@xref{Connecting}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Transport endpoint is not connected
|
|
@deftypevr Macro int ENOTCONN
|
|
@comment errno 57 @c DO NOT REMOVE
|
|
The socket is not connected to anything. You get this error when you
|
|
try to transmit data over a socket, without first specifying a
|
|
destination for the data. For a connectionless socket (for datagram
|
|
protocols, such as UDP), you get @code{EDESTADDRREQ} instead.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Destination address required
|
|
@deftypevr Macro int EDESTADDRREQ
|
|
@comment errno 39 @c DO NOT REMOVE
|
|
No default destination address was set for the socket. You get this
|
|
error when you try to transmit data over a connectionless socket,
|
|
without first specifying a destination for the data with @code{connect}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Cannot send after transport endpoint shutdown
|
|
@deftypevr Macro int ESHUTDOWN
|
|
@comment errno 58 @c DO NOT REMOVE
|
|
The socket has already been shut down.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Too many references: cannot splice
|
|
@deftypevr Macro int ETOOMANYREFS
|
|
@comment errno 59 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Connection timed out
|
|
@deftypevr Macro int ETIMEDOUT
|
|
@comment errno 60 @c DO NOT REMOVE
|
|
A socket operation with a specified timeout received no response during
|
|
the timeout period.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Connection refused
|
|
@deftypevr Macro int ECONNREFUSED
|
|
@comment errno 61 @c DO NOT REMOVE
|
|
A remote host refused to allow the network connection (typically because
|
|
it is not running the requested service).
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Too many levels of symbolic links
|
|
@deftypevr Macro int ELOOP
|
|
@comment errno 62 @c DO NOT REMOVE
|
|
Too many levels of symbolic links were encountered in looking up a file name.
|
|
This often indicates a cycle of symbolic links.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: File name too long
|
|
@deftypevr Macro int ENAMETOOLONG
|
|
@comment errno 63 @c DO NOT REMOVE
|
|
Filename too long (longer than @code{PATH_MAX}; @pxref{Limits for
|
|
Files}) or host name too long (in @code{gethostname} or
|
|
@code{sethostname}; @pxref{Host Identification}).
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Host is down
|
|
@deftypevr Macro int EHOSTDOWN
|
|
@comment errno 64 @c DO NOT REMOVE
|
|
The remote host for a requested network connection is down.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: No route to host
|
|
@deftypevr Macro int EHOSTUNREACH
|
|
@comment errno 65 @c DO NOT REMOVE
|
|
The remote host for a requested network connection is not reachable.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: Directory not empty
|
|
@deftypevr Macro int ENOTEMPTY
|
|
@comment errno 66 @c DO NOT REMOVE
|
|
Directory not empty, where an empty directory was expected. Typically,
|
|
this error occurs when you are trying to delete a directory.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Too many processes
|
|
@deftypevr Macro int EPROCLIM
|
|
@comment errno 67 @c DO NOT REMOVE
|
|
This means that the per-user limit on new process would be exceeded by
|
|
an attempted @code{fork}. @xref{Limits on Resources}, for details on
|
|
the @code{RLIMIT_NPROC} limit.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Too many users
|
|
@deftypevr Macro int EUSERS
|
|
@comment errno 68 @c DO NOT REMOVE
|
|
The file quota system is confused because there are too many users.
|
|
@c This can probably happen in a GNU system when using NFS.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Disk quota exceeded
|
|
@deftypevr Macro int EDQUOT
|
|
@comment errno 69 @c DO NOT REMOVE
|
|
The user's disk quota was exceeded.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Stale NFS file handle
|
|
@deftypevr Macro int ESTALE
|
|
@comment errno 70 @c DO NOT REMOVE
|
|
Stale NFS file handle. This indicates an internal confusion in the NFS
|
|
system which is due to file system rearrangements on the server host.
|
|
Repairing this condition usually requires unmounting and remounting
|
|
the NFS file system on the local host.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Object is remote
|
|
@deftypevr Macro int EREMOTE
|
|
@comment errno 71 @c DO NOT REMOVE
|
|
An attempt was made to NFS-mount a remote file system with a file name that
|
|
already specifies an NFS-mounted file.
|
|
(This is an error on some operating systems, but we expect it to work
|
|
properly on the GNU system, making this error code impossible.)
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: RPC struct is bad
|
|
@deftypevr Macro int EBADRPC
|
|
@comment errno 72 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: RPC version wrong
|
|
@deftypevr Macro int ERPCMISMATCH
|
|
@comment errno 73 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: RPC program not available
|
|
@deftypevr Macro int EPROGUNAVAIL
|
|
@comment errno 74 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: RPC program version wrong
|
|
@deftypevr Macro int EPROGMISMATCH
|
|
@comment errno 75 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: RPC bad procedure for program
|
|
@deftypevr Macro int EPROCUNAVAIL
|
|
@comment errno 76 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: No locks available
|
|
@deftypevr Macro int ENOLCK
|
|
@comment errno 77 @c DO NOT REMOVE
|
|
No locks available. This is used by the file locking facilities; see
|
|
@ref{File Locks}. This error is never generated by the GNU system, but
|
|
it can result from an operation to an NFS server running another
|
|
operating system.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Inappropriate file type or format
|
|
@deftypevr Macro int EFTYPE
|
|
@comment errno 79 @c DO NOT REMOVE
|
|
Inappropriate file type or format. The file was the wrong type for the
|
|
operation, or a data file had the wrong format.
|
|
|
|
On some systems @code{chmod} returns this error if you try to set the
|
|
sticky bit on a non-directory file; @pxref{Setting Permissions}.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Authentication error
|
|
@deftypevr Macro int EAUTH
|
|
@comment errno 80 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment BSD: Need authenticator
|
|
@deftypevr Macro int ENEEDAUTH
|
|
@comment errno 81 @c DO NOT REMOVE
|
|
???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: Function not implemented
|
|
@deftypevr Macro int ENOSYS
|
|
@comment errno 78 @c DO NOT REMOVE
|
|
Function not implemented. This indicates that the function called is
|
|
not implemented at all, either in the C library itself or in the
|
|
operating system. When you get this error, you can be sure that this
|
|
particular function will always fail with @code{ENOSYS} unless you
|
|
install a new version of the C library or the operating system.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: Not supported
|
|
@deftypevr Macro int ENOTSUP
|
|
@comment errno 118 @c DO NOT REMOVE
|
|
Not supported. A function returns this error when certain parameter
|
|
values are valid, but the functionality they request is not available.
|
|
This can mean that the function does not implement a particular command
|
|
or option value or flag bit at all. For functions that operate on some
|
|
object given in a parameter, such as a file descriptor or a port, it
|
|
might instead mean that only @emph{that specific object} (file
|
|
descriptor, port, etc.) is unable to support the other parameters given;
|
|
different file descriptors might support different ranges of parameter
|
|
values.
|
|
|
|
If the entire function is not available at all in the implementation,
|
|
it returns @code{ENOSYS} instead.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment ISO: Invalid or incomplete multibyte or wide character
|
|
@deftypevr Macro int EILSEQ
|
|
@comment errno 106 @c DO NOT REMOVE
|
|
While decoding a multibyte character the function came along an invalid
|
|
or an incomplete sequence of bytes or the given wide character is invalid.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment GNU: Inappropriate operation for background process
|
|
@deftypevr Macro int EBACKGROUND
|
|
@comment errno 100 @c DO NOT REMOVE
|
|
In the GNU system, servers supporting the @code{term} protocol return
|
|
this error for certain operations when the caller is not in the
|
|
foreground process group of the terminal. Users do not usually see this
|
|
error because functions such as @code{read} and @code{write} translate
|
|
it into a @code{SIGTTIN} or @code{SIGTTOU} signal. @xref{Job Control},
|
|
for information on process groups and these signals.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment GNU: Translator died
|
|
@deftypevr Macro int EDIED
|
|
@comment errno 101 @c DO NOT REMOVE
|
|
In the GNU system, opening a file returns this error when the file is
|
|
translated by a program and the translator program dies while starting
|
|
up, before it has connected to the file.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment GNU: ?
|
|
@deftypevr Macro int ED
|
|
@comment errno 102 @c DO NOT REMOVE
|
|
The experienced user will know what is wrong.
|
|
@c This error code is a joke. Its perror text is part of the joke.
|
|
@c Don't change it.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment GNU: You really blew it this time
|
|
@deftypevr Macro int EGREGIOUS
|
|
@comment errno 103 @c DO NOT REMOVE
|
|
You did @strong{what}?
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment GNU: Computer bought the farm
|
|
@deftypevr Macro int EIEIO
|
|
@comment errno 104 @c DO NOT REMOVE
|
|
Go home and have a glass of warm, dairy-fresh milk.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment GNU: Gratuitous error
|
|
@deftypevr Macro int EGRATUITOUS
|
|
@comment errno 105 @c DO NOT REMOVE
|
|
This error code has no purpose.
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Bad message
|
|
@deftypevr Macro int EBADMSG
|
|
@comment errno 107
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Identifier removed
|
|
@deftypevr Macro int EIDRM
|
|
@comment errno 108
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Multihop attempted
|
|
@deftypevr Macro int EMULTIHOP
|
|
@comment errno 109
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: No data available
|
|
@deftypevr Macro int ENODATA
|
|
@comment errno 110
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Link has been severed
|
|
@deftypevr Macro int ENOLINK
|
|
@comment errno 111
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: No message of desired type
|
|
@deftypevr Macro int ENOMSG
|
|
@comment errno 112
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Out of streams resources
|
|
@deftypevr Macro int ENOSR
|
|
@comment errno 113
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Device not a stream
|
|
@deftypevr Macro int ENOSTR
|
|
@comment errno 114
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Value too large for defined data type
|
|
@deftypevr Macro int EOVERFLOW
|
|
@comment errno 115
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Protocol error
|
|
@deftypevr Macro int EPROTO
|
|
@comment errno 116
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment XOPEN: Timer expired
|
|
@deftypevr Macro int ETIME
|
|
@comment errno 117
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment POSIX.1: Operation canceled
|
|
@deftypevr Macro int ECANCELED
|
|
@comment errno 118
|
|
Operation canceled; an asynchronous operation was canceled before it
|
|
completed. @xref{Asynchronous I/O}. When you call @code{aio_cancel},
|
|
the normal result is for the operations affected to complete with this
|
|
error; @pxref{Cancel AIO Operations}.
|
|
@end deftypevr
|
|
|
|
|
|
@emph{The following error codes are defined by the Linux/i386 kernel.
|
|
They are not yet documented.}
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Interrupted system call should be restarted
|
|
@deftypevr Macro int ERESTART
|
|
@comment errno ???/85
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Channel number out of range
|
|
@deftypevr Macro int ECHRNG
|
|
@comment errno ???/44
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Obsolete: Level 2 not synchronized
|
|
@deftypevr Macro int EL2NSYNC
|
|
@comment errno ???/45
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Obsolete: Level 3 halted
|
|
@deftypevr Macro int EL3HLT
|
|
@comment errno ???/46
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Obsolete: Level 3 reset
|
|
@deftypevr Macro int EL3RST
|
|
@comment errno ???/47
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Link number out of range
|
|
@deftypevr Macro int ELNRNG
|
|
@comment errno ???/48
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Protocol driver not attached
|
|
@deftypevr Macro int EUNATCH
|
|
@comment errno ???/49
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: No CSI structure available
|
|
@deftypevr Macro int ENOCSI
|
|
@comment errno ???/50
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Obsolete: Level 2 halted
|
|
@deftypevr Macro int EL2HLT
|
|
@comment errno ???/51
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Invalid exchange
|
|
@deftypevr Macro int EBADE
|
|
@comment errno ???/52
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Invalid request descriptor
|
|
@deftypevr Macro int EBADR
|
|
@comment errno ???/53
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Exchange full
|
|
@deftypevr Macro int EXFULL
|
|
@comment errno ???/54
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: No anode
|
|
@deftypevr Macro int ENOANO
|
|
@comment errno ???/55
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Invalid request code
|
|
@deftypevr Macro int EBADRQC
|
|
@comment errno ???/56
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Invalid slot
|
|
@deftypevr Macro int EBADSLT
|
|
@comment errno ???/57
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: File locking deadlock error
|
|
@deftypevr Macro int EDEADLOCK
|
|
@comment errno ???/58
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Bad font file format
|
|
@deftypevr Macro int EBFONT
|
|
@comment errno ???/59
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Machine is not on the network
|
|
@deftypevr Macro int ENONET
|
|
@comment errno ???/64
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Package not installed
|
|
@deftypevr Macro int ENOPKG
|
|
@comment errno ???/65
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Advertise error
|
|
@deftypevr Macro int EADV
|
|
@comment errno ???/68
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Srmount error
|
|
@deftypevr Macro int ESRMNT
|
|
@comment errno ???/69
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Communication error on send
|
|
@deftypevr Macro int ECOMM
|
|
@comment errno ???/70
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: RFS specific error
|
|
@deftypevr Macro int EDOTDOT
|
|
@comment errno ???/73
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Name not unique on network
|
|
@deftypevr Macro int ENOTUNIQ
|
|
@comment errno ???/76
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: File descriptor in bad state
|
|
@deftypevr Macro int EBADFD
|
|
@comment errno ???/77
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Remote address changed
|
|
@deftypevr Macro int EREMCHG
|
|
@comment errno ???/78
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Can not access a needed shared library
|
|
@deftypevr Macro int ELIBACC
|
|
@comment errno ???/79
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Accessing a corrupted shared library
|
|
@deftypevr Macro int ELIBBAD
|
|
@comment errno ???/80
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: .lib section in a.out corrupted
|
|
@deftypevr Macro int ELIBSCN
|
|
@comment errno ???/81
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Attempting to link in too many shared libraries
|
|
@deftypevr Macro int ELIBMAX
|
|
@comment errno ???/82
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Cannot exec a shared library directly
|
|
@deftypevr Macro int ELIBEXEC
|
|
@comment errno ???/83
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Streams pipe error
|
|
@deftypevr Macro int ESTRPIPE
|
|
@comment errno ???/86
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Structure needs cleaning
|
|
@deftypevr Macro int EUCLEAN
|
|
@comment errno ???/117
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Not a XENIX named type file
|
|
@deftypevr Macro int ENOTNAM
|
|
@comment errno ???/118
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: No XENIX semaphores available
|
|
@deftypevr Macro int ENAVAIL
|
|
@comment errno ???/119
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Is a named type file
|
|
@deftypevr Macro int EISNAM
|
|
@comment errno ???/120
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Remote I/O error
|
|
@deftypevr Macro int EREMOTEIO
|
|
@comment errno ???/121
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: No medium found
|
|
@deftypevr Macro int ENOMEDIUM
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux???: Wrong medium type
|
|
@deftypevr Macro int EMEDIUMTYPE
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: Required key not available
|
|
@deftypevr Macro int ENOKEY
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: Key has expired
|
|
@deftypevr Macro int EKEYEXPIRED
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: Key has been revoked
|
|
@deftypevr Macro int EKEYREVOKED
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: Key was rejected by service
|
|
@deftypevr Macro int EKEYREJECTED
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: Owner died
|
|
@deftypevr Macro int EOWNERDEAD
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@comment errno.h
|
|
@comment Linux: State not recoverable
|
|
@deftypevr Macro int ENOTRECOVERABLE
|
|
@comment errno ???/???
|
|
@end deftypevr
|
|
|
|
@node Error Messages, , Error Codes, Error Reporting
|
|
@section Error Messages
|
|
|
|
The library has functions and variables designed to make it easy for
|
|
your program to report informative error messages in the customary
|
|
format about the failure of a library call. The functions
|
|
@code{strerror} and @code{perror} give you the standard error message
|
|
for a given error code; the variable
|
|
@w{@code{program_invocation_short_name}} gives you convenient access to the
|
|
name of the program that encountered the error.
|
|
|
|
@comment string.h
|
|
@comment ISO
|
|
@deftypefun {char *} strerror (int @var{errnum})
|
|
The @code{strerror} function maps the error code (@pxref{Checking for
|
|
Errors}) specified by the @var{errnum} argument to a descriptive error
|
|
message string. The return value is a pointer to this string.
|
|
|
|
The value @var{errnum} normally comes from the variable @code{errno}.
|
|
|
|
You should not modify the string returned by @code{strerror}. Also, if
|
|
you make subsequent calls to @code{strerror}, the string might be
|
|
overwritten. (But it's guaranteed that no library function ever calls
|
|
@code{strerror} behind your back.)
|
|
|
|
The function @code{strerror} is declared in @file{string.h}.
|
|
@end deftypefun
|
|
|
|
@comment string.h
|
|
@comment GNU
|
|
@deftypefun {char *} strerror_r (int @var{errnum}, char *@var{buf}, size_t @var{n})
|
|
The @code{strerror_r} function works like @code{strerror} but instead of
|
|
returning the error message in a statically allocated buffer shared by
|
|
all threads in the process, it returns a private copy for the
|
|
thread. This might be either some permanent global data or a message
|
|
string in the user supplied buffer starting at @var{buf} with the
|
|
length of @var{n} bytes.
|
|
|
|
At most @var{n} characters are written (including the NUL byte) so it is
|
|
up to the user to select the buffer large enough.
|
|
|
|
This function should always be used in multi-threaded programs since
|
|
there is no way to guarantee the string returned by @code{strerror}
|
|
really belongs to the last call of the current thread.
|
|
|
|
This function @code{strerror_r} is a GNU extension and it is declared in
|
|
@file{string.h}.
|
|
@end deftypefun
|
|
|
|
@comment stdio.h
|
|
@comment ISO
|
|
@deftypefun void perror (const char *@var{message})
|
|
This function prints an error message to the stream @code{stderr};
|
|
see @ref{Standard Streams}. The orientation of @code{stderr} is not
|
|
changed.
|
|
|
|
If you call @code{perror} with a @var{message} that is either a null
|
|
pointer or an empty string, @code{perror} just prints the error message
|
|
corresponding to @code{errno}, adding a trailing newline.
|
|
|
|
If you supply a non-null @var{message} argument, then @code{perror}
|
|
prefixes its output with this string. It adds a colon and a space
|
|
character to separate the @var{message} from the error string corresponding
|
|
to @code{errno}.
|
|
|
|
The function @code{perror} is declared in @file{stdio.h}.
|
|
@end deftypefun
|
|
|
|
@code{strerror} and @code{perror} produce the exact same message for any
|
|
given error code; the precise text varies from system to system. On the
|
|
GNU system, the messages are fairly short; there are no multi-line
|
|
messages or embedded newlines. Each error message begins with a capital
|
|
letter and does not include any terminating punctuation.
|
|
|
|
@strong{Compatibility Note:} The @code{strerror} function was introduced
|
|
in @w{ISO C89}. Many older C systems do not support this function yet.
|
|
|
|
@cindex program name
|
|
@cindex name of running program
|
|
Many programs that don't read input from the terminal are designed to
|
|
exit if any system call fails. By convention, the error message from
|
|
such a program should start with the program's name, sans directories.
|
|
You can find that name in the variable
|
|
@code{program_invocation_short_name}; the full file name is stored the
|
|
variable @code{program_invocation_name}.
|
|
|
|
@comment errno.h
|
|
@comment GNU
|
|
@deftypevar {char *} program_invocation_name
|
|
This variable's value is the name that was used to invoke the program
|
|
running in the current process. It is the same as @code{argv[0]}. Note
|
|
that this is not necessarily a useful file name; often it contains no
|
|
directory names. @xref{Program Arguments}.
|
|
@end deftypevar
|
|
|
|
@comment errno.h
|
|
@comment GNU
|
|
@deftypevar {char *} program_invocation_short_name
|
|
This variable's value is the name that was used to invoke the program
|
|
running in the current process, with directory names removed. (That is
|
|
to say, it is the same as @code{program_invocation_name} minus
|
|
everything up to the last slash, if any.)
|
|
@end deftypevar
|
|
|
|
The library initialization code sets up both of these variables before
|
|
calling @code{main}.
|
|
|
|
@strong{Portability Note:} These two variables are GNU extensions. If
|
|
you want your program to work with non-GNU libraries, you must save the
|
|
value of @code{argv[0]} in @code{main}, and then strip off the directory
|
|
names yourself. We added these extensions to make it possible to write
|
|
self-contained error-reporting subroutines that require no explicit
|
|
cooperation from @code{main}.
|
|
|
|
Here is an example showing how to handle failure to open a file
|
|
correctly. The function @code{open_sesame} tries to open the named file
|
|
for reading and returns a stream if successful. The @code{fopen}
|
|
library function returns a null pointer if it couldn't open the file for
|
|
some reason. In that situation, @code{open_sesame} constructs an
|
|
appropriate error message using the @code{strerror} function, and
|
|
terminates the program. If we were going to make some other library
|
|
calls before passing the error code to @code{strerror}, we'd have to
|
|
save it in a local variable instead, because those other library
|
|
functions might overwrite @code{errno} in the meantime.
|
|
|
|
@smallexample
|
|
#include <errno.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
|
|
FILE *
|
|
open_sesame (char *name)
|
|
@{
|
|
FILE *stream;
|
|
|
|
errno = 0;
|
|
stream = fopen (name, "r");
|
|
if (stream == NULL)
|
|
@{
|
|
fprintf (stderr, "%s: Couldn't open file %s; %s\n",
|
|
program_invocation_short_name, name, strerror (errno));
|
|
exit (EXIT_FAILURE);
|
|
@}
|
|
else
|
|
return stream;
|
|
@}
|
|
@end smallexample
|
|
|
|
Using @code{perror} has the advantage that the function is portable and
|
|
available on all systems implementing @w{ISO C}. But often the text
|
|
@code{perror} generates is not what is wanted and there is no way to
|
|
extend or change what @code{perror} does. The GNU coding standard, for
|
|
instance, requires error messages to be preceded by the program name and
|
|
programs which read some input files should should provide information
|
|
about the input file name and the line number in case an error is
|
|
encountered while reading the file. For these occasions there are two
|
|
functions available which are widely used throughout the GNU project.
|
|
These functions are declared in @file{error.h}.
|
|
|
|
@comment error.h
|
|
@comment GNU
|
|
@deftypefun void error (int @var{status}, int @var{errnum}, const char *@var{format}, @dots{})
|
|
The @code{error} function can be used to report general problems during
|
|
program execution. The @var{format} argument is a format string just
|
|
like those given to the @code{printf} family of functions. The
|
|
arguments required for the format can follow the @var{format} parameter.
|
|
Just like @code{perror}, @code{error} also can report an error code in
|
|
textual form. But unlike @code{perror} the error value is explicitly
|
|
passed to the function in the @var{errnum} parameter. This elimintates
|
|
the problem mentioned above that the error reporting function must be
|
|
called immediately after the function causing the error since otherwise
|
|
@code{errno} might have a different value.
|
|
|
|
The @code{error} prints first the program name. If the application
|
|
defined a global variable @code{error_print_progname} and points it to a
|
|
function this function will be called to print the program name.
|
|
Otherwise the string from the global variable @code{program_name} is
|
|
used. The program name is followed by a colon and a space which in turn
|
|
is followed by the output produced by the format string. If the
|
|
@var{errnum} parameter is non-zero the format string output is followed
|
|
by a colon and a space, followed by the error message for the error code
|
|
@var{errnum}. In any case is the output terminated with a newline.
|
|
|
|
The output is directed to the @code{stderr} stream. If the
|
|
@code{stderr} wasn't oriented before the call it will be narrow-oriented
|
|
afterwards.
|
|
|
|
The function will return unless the @var{status} parameter has a
|
|
non-zero value. In this case the function will call @code{exit} with
|
|
the @var{status} value for its parameter and therefore never return. If
|
|
@code{error} returns the global variable @code{error_message_count} is
|
|
incremented by one to keep track of the number of errors reported.
|
|
@end deftypefun
|
|
|
|
@comment error.h
|
|
@comment GNU
|
|
@deftypefun void error_at_line (int @var{status}, int @var{errnum}, const char *@var{fname}, unsigned int @var{lineno}, const char *@var{format}, @dots{})
|
|
|
|
The @code{error_at_line} function is very similar to the @code{error}
|
|
function. The only difference are the additional parameters @var{fname}
|
|
and @var{lineno}. The handling of the other parameters is identical to
|
|
that of @code{error} except that between the program name and the string
|
|
generated by the format string additional text is inserted.
|
|
|
|
Directly following the program name a colon, followed by the file name
|
|
pointer to by @var{fname}, another colon, and a value of @var{lineno} is
|
|
printed.
|
|
|
|
This additional output of course is meant to be used to locate an error
|
|
in an input file (like a programming language source code file etc).
|
|
|
|
If the global variable @code{error_one_per_line} is set to a non-zero
|
|
value @code{error_at_line} will avoid printing consecutive messages for
|
|
the same file anem line. Repetition which are not directly following
|
|
each other are not caught.
|
|
|
|
Just like @code{error} this function only returned if @var{status} is
|
|
zero. Otherwise @code{exit} is called with the non-zero value. If
|
|
@code{error} returns the global variable @code{error_message_count} is
|
|
incremented by one to keep track of the number of errors reported.
|
|
@end deftypefun
|
|
|
|
As mentioned above the @code{error} and @code{error_at_line} functions
|
|
can be customized by defining a variable named
|
|
@code{error_print_progname}.
|
|
|
|
@comment error.h
|
|
@comment GNU
|
|
@deftypevar {void (*} error_print_progname ) (void)
|
|
If the @code{error_print_progname} variable is defined to a non-zero
|
|
value the function pointed to is called by @code{error} or
|
|
@code{error_at_line}. It is expected to print the program name or do
|
|
something similarly useful.
|
|
|
|
The function is expected to be print to the @code{stderr} stream and
|
|
must be able to handle whatever orientation the stream has.
|
|
|
|
The variable is global and shared by all threads.
|
|
@end deftypevar
|
|
|
|
@comment error.h
|
|
@comment GNU
|
|
@deftypevar {unsigned int} error_message_count
|
|
The @code{error_message_count} variable is incremented whenever one of
|
|
the functions @code{error} or @code{error_at_line} returns. The
|
|
variable is global and shared by all threads.
|
|
@end deftypevar
|
|
|
|
@comment error.h
|
|
@comment GNU
|
|
@deftypevar int error_one_per_line
|
|
The @code{error_one_per_line} variable influences only
|
|
@code{error_at_line}. Normally the @code{error_at_line} function
|
|
creates output for every invocation. If @code{error_one_per_line} is
|
|
set to a non-zero value @code{error_at_line} keeps track of the last
|
|
file name and line number for which an error was reported and avoid
|
|
directly following messages for the same file and line. This variable
|
|
is global and shared by all threads.
|
|
@end deftypevar
|
|
|
|
@noindent
|
|
A program which read some input file and reports errors in it could look
|
|
like this:
|
|
|
|
@smallexample
|
|
@{
|
|
char *line = NULL;
|
|
size_t len = 0;
|
|
unsigned int lineno = 0;
|
|
|
|
error_message_count = 0;
|
|
while (! feof_unlocked (fp))
|
|
@{
|
|
ssize_t n = getline (&line, &len, fp);
|
|
if (n <= 0)
|
|
/* @r{End of file or error.} */
|
|
break;
|
|
++lineno;
|
|
|
|
/* @r{Process the line.} */
|
|
@dots{}
|
|
|
|
if (@r{Detect error in line})
|
|
error_at_line (0, errval, filename, lineno,
|
|
"some error text %s", some_variable);
|
|
@}
|
|
|
|
if (error_message_count != 0)
|
|
error (EXIT_FAILURE, 0, "%u errors found", error_message_count);
|
|
@}
|
|
@end smallexample
|
|
|
|
@code{error} and @code{error_at_line} are clearly the functions of
|
|
choice and enable the programmer to write applications which follow the
|
|
GNU coding standard. The GNU libc additionally contains functions which
|
|
are used in BSD for the same purpose. These functions are declared in
|
|
@file{err.h}. It is generally advised to not use these functions. They
|
|
are included only for compatibility.
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void warn (const char *@var{format}, @dots{})
|
|
The @code{warn} function is roughly equivalent to a call like
|
|
@smallexample
|
|
error (0, errno, format, @r{the parameters})
|
|
@end smallexample
|
|
@noindent
|
|
except that the global variables @code{error} respects and modifies
|
|
are not used.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void vwarn (const char *@var{format}, va_list)
|
|
The @code{vwarn} function is just like @code{warn} except that the
|
|
parameters for the handling of the format string @var{format} are passed
|
|
in as an value of type @code{va_list}.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void warnx (const char *@var{format}, @dots{})
|
|
The @code{warnx} function is roughly equivalent to a call like
|
|
@smallexample
|
|
error (0, 0, format, @r{the parameters})
|
|
@end smallexample
|
|
@noindent
|
|
except that the global variables @code{error} respects and modifies
|
|
are not used. The difference to @code{warn} is that no error number
|
|
string is printed.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void vwarnx (const char *@var{format}, va_list)
|
|
The @code{vwarnx} function is just like @code{warnx} except that the
|
|
parameters for the handling of the format string @var{format} are passed
|
|
in as an value of type @code{va_list}.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void err (int @var{status}, const char *@var{format}, @dots{})
|
|
The @code{err} function is roughly equivalent to a call like
|
|
@smallexample
|
|
error (status, errno, format, @r{the parameters})
|
|
@end smallexample
|
|
@noindent
|
|
except that the global variables @code{error} respects and modifies
|
|
are not used and that the program is exited even if @var{status} is zero.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void verr (int @var{status}, const char *@var{format}, va_list)
|
|
The @code{verr} function is just like @code{err} except that the
|
|
parameters for the handling of the format string @var{format} are passed
|
|
in as an value of type @code{va_list}.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void errx (int @var{status}, const char *@var{format}, @dots{})
|
|
The @code{errx} function is roughly equivalent to a call like
|
|
@smallexample
|
|
error (status, 0, format, @r{the parameters})
|
|
@end smallexample
|
|
@noindent
|
|
except that the global variables @code{error} respects and modifies
|
|
are not used and that the program is exited even if @var{status}
|
|
is zero. The difference to @code{err} is that no error number
|
|
string is printed.
|
|
@end deftypefun
|
|
|
|
@comment err.h
|
|
@comment BSD
|
|
@deftypefun void verrx (int @var{status}, const char *@var{format}, va_list)
|
|
The @code{verrx} function is just like @code{errx} except that the
|
|
parameters for the handling of the format string @var{format} are passed
|
|
in as an value of type @code{va_list}.
|
|
@end deftypefun
|