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NAME |LIBRARY |SYNOPSIS |DESCRIPTION |ATTRIBUTES |STANDARDS |HISTORY |SEE ALSO |COLOPHON | |
perror(3) Library Functions Manualperror(3)perror - print a system error message
Standard C library (libc,-lc)
#include <stdio.h>void perror(const char *s);#include <errno.h>interrno;/* Not really declared this way; see errno(3) */[[deprecated]] const char *constsys_errlist[];[[deprecated]] intsys_nerr; Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):sys_errlist,sys_nerr: From glibc 2.19 to glibc 2.31: _DEFAULT_SOURCE glibc 2.19 and earlier: _BSD_SOURCE
Theperror() function produces a message on standard error describing the last error encountered during a call to a system or library function. First (ifs is not NULL and*s is not a null byte ('\0')), the argument strings is printed, followed by a colon and a blank. Then an error message corresponding to the current value oferrno 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 listsys_errlist[], which can be indexed byerrno, can be used to obtain the error message without the newline. The largest message number provided in the table issys_nerr-1. Be careful when directly accessing this list, because new error values may not have been added tosys_errlist[]. The use ofsys_errlist[] is nowadays deprecated; usestrerror(3) instead. When a system call fails, it usually returns -1 and sets the variableerrno to a value describing what went wrong. (These values can be found in<errno.h>.) Many library functions do likewise. The functionperror() serves to translate this error code into human-readable form. Note thaterrno 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 toperror(), the value oferrno should be saved.For an explanation of the terms used in this section, seeattributes(7). ┌──────────────────────────┬───────────────┬─────────────────────┐ │Interface│Attribute│Value│ ├──────────────────────────┼───────────────┼─────────────────────┤ │perror() │ Thread safety │ MT-Safe race:stderr │ └──────────────────────────┴───────────────┴─────────────────────┘
errnoperror() C11, POSIX.1-2008.sys_nerrsys_errlist BSD.
errnoperror() POSIX.1-2001, C89, 4.3BSD.sys_nerrsys_errlist Removed in glibc 2.32.
err(3),errno(3),error(3),strerror(3)
This page is part of theman-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-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. 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 isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17perror(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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