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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | ATTRIBUTES | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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perror(3) Library Functions Manual perror(3)
perror - print a system error message
Standard C library (libc, -lc)
#include <stdio.h>
void perror(const char *s);
#include <errno.h>
int errno; /* Not really declared this way; see errno(3) */
[[deprecated]] const char *const sys_errlist[];
[[deprecated]] int sys_nerr;
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
sys_errlist, sys_nerr:
From glibc 2.19 to glibc 2.31:
_DEFAULT_SOURCE
glibc 2.19 and earlier:
_BSD_SOURCE
The perror() function produces a message on standard error
describing the last error encountered during a call to a system
or library function.
First (if s is not NULL and *s is not a null byte ('\0')), the
argument string s is printed, followed by a colon and a blank.
Then an error message corresponding to the current value of errno
and a new-line.
To be of most use, the argument string should include the name of
the function that incurred the error.
The global error list sys_errlist[], which can be indexed by
errno, can be used to obtain the error message without the
newline. The largest message number provided in the table is
sys_nerr-1. Be careful when directly accessing this list,
because new error values may not have been added to
sys_errlist[]. The use of sys_errlist[] is nowadays deprecated;
use strerror(3) instead.
When a system call fails, it usually returns -1 and sets the
variable errno to a value describing what went wrong. (These
values can be found in <errno.h>.) Many library functions do
likewise. The function perror() serves to translate this error
code into human-readable form. Note that errno is undefined
after a successful system call or library function call: this
call may well change this variable, even though it succeeds, for
example because it internally used some other library function
that failed. Thus, if a failing call is not immediately followed
by a call to perror(), the value of errno should be saved.
For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────┬───────────────┬─────────────────────┐
│ Interface │ Attribute │ Value │
├─────────────────────────┼───────────────┼─────────────────────┤
│ perror() │ Thread safety │ MT-Safe race:stderr │
└─────────────────────────┴───────────────┴─────────────────────┘
errno
perror()
C11, POSIX.1-2008.
sys_nerr
sys_errlist
BSD.
errno
perror()
POSIX.1-2001, C89, 4.3BSD.
sys_nerr
sys_errlist
Removed in glibc 2.32.
err(3), errno(3), error(3), strerror(3)
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-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. 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
[email protected]
Linux man-pages 6.9.1 2024-06-15 perror(3)
Pages that refer to this page: err(3), errno(3), error(3), fmtmsg(3), pmerrstr(3), psignal(3), sd_journal_print(3), stdio(3), strerror(3)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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