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error(3) — Linux manual page

error(3) Library Functions Manual error(3)

NAME top

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

LIBRARY top

 Standard C library (libc, -lc)

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 typeof(void (void)) *error_print_progname;

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;
 otherwise it returns after printing the error message.
 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
 attributes(7).
 ┌─────────────────┬───────────────┬──────────────────────────────┐
 │ 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 cancelation, so it can be interrupted only
 after one of the two variables is modified. After that,
 error_at_line() is very much like error().

STANDARDS top

 GNU.

SEE ALSO top

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

COLOPHON top

 This page is part of the man-pages (Linux kernel and C library
 user-space interface documentation) project. Information about
 the project can be found at 
 ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
 for this manual page, see
 ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
 This page was obtained from the tarball man-pages-6.10.tar.gz
 fetched from
 ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
 2025年02月02日. If you discover any rendering problems in this HTML
 version of the page, or you believe there is a better or more up-
 to-date source for the page, or you have corrections or
 improvements to the information in this COLOPHON (which is not
 part of the original manual page), send a mail to
 man-pages@man7.org
Linux man-pages 6.10 2024年12月13日 error(3)

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Pages that refer to this page: err(3), errno(3), perror(3), strerror(3), sysexits.h(3head)

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