error(3) — Linux manual page


ERROR(3)                  Linux Programmer's Manual                 ERROR(3)

NAME         top

       error,    error_at_line,   error_message_count,   error_one_per_line,
       error_print_progname - glibc error reporting functions

SYNOPSIS         top

       #include <error.h>

       void error(int status, int errnum, const char *format, ...);

       void error_at_line(int status, int errnum, const char *filename,
                          unsigned int linenum, const char *format, ...);

       extern unsigned int error_message_count;

       extern int error_one_per_line;

       extern void (*error_print_progname) (void);

DESCRIPTION         top

       error() is a general error-reporting function.  It flushes stdout,
       and then outputs to stderr the program name, a colon and a space, the
       message specified by the printf(3)-style format string format, and,
       if errnum is nonzero, a second colon and a space followed by the
       string given by strerror(errnum).  Any arguments required for format
       should follow format in the argument list.  The output is terminated
       by a newline character.

       The program name printed by error() is the value of the global
       variable program_invocation_name(3).  program_invocation_name
       initially has the same value as main()'s argv[0].  The value of this
       variable can be modified to change the output of error().

       If status has a nonzero value, then error() calls exit(3) to
       terminate the program using the given value as the exit status.

       The error_at_line() function is exactly the same as error(), except
       for the addition of the arguments filename and linenum.  The output
       produced is as for error(), except that after the program name are
       written: a colon, the value of filename, a colon, and the value of
       linenum.  The preprocessor values __LINE__ and __FILE__ may be useful
       when calling error_at_line(), but other values can also be used.  For
       example, these arguments could refer to a location in an input file.

       If the global variable error_one_per_line is set nonzero, a sequence
       of error_at_line() calls with the same value of filename and linenum
       will result in only one message (the first) being output.

       The global variable error_message_count counts the number of messages
       that have been output by error() and error_at_line().

       If the global variable error_print_progname is assigned the address
       of a function (i.e., is not NULL), then that function is called
       instead of prefixing the message with the program name and colon.
       The function should print a suitable string to stderr.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface       Attribute     Value                             │
       │error()         │ Thread safety │ MT-Safe locale                    │
       │error_at_line() │ Thread safety │ MT-Unsafe race:                   │
       │                │               │ error_at_line/error_one_per_line  │
       │                │               │ locale                            │
       The  internal  error_one_per_line  variable  is accessed (without any
       form of synchronization, but since it's an int used once,  it  should
       be  safe  enough)  and,  if  error_one_per_line  is  set nonzero, the
       internal static variables (not exposed to users)  used  to  hold  the
       last  printed  filename  and  line  number  are accessed and modified
       without synchronization; the update  is  not  atomic  and  it  occurs
       before  disabling  cancellation,  so it can be interrupted only after
       one of the two variables is modified.  After that, error_at_line() is
       very much like error().

CONFORMING TO         top

       These functions and variables are GNU extensions, and should not be
       used in programs intended to be portable.

SEE ALSO         top

       err(3), errno(3), exit(3), perror(3), program_invocation_name(3),

COLOPHON         top

       This page is part of release 5.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

GNU                              2017-09-15                         ERROR(3)

Pages that refer to this page: err(3)errno(3)errx(3)perror(3)strerror(3)strerror_l(3)strerror_r(3)sys_errlist(3)sys_nerr(3)verr(3)verrx(3)vwarn(3)vwarnx(3)warn(3)warnx(3)