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   perror    ( 3 )

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Имя (Name)

perror - print a system error message

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Синопсис (Synopsis)

#include <stdio.h>

       void perror(const char *s);

       #include <errno.h>

       const char *const sys_errlist[];
       int sys_nerr;
       int errno;       /* Not really declared this way; see errno(3) */

   Feature Test Macro Requirements for glibc (see
   feature_test_macros(7)):

       sys_errlist, sys_nerr:
           From glibc 2.19 to 2.31:
               _DEFAULT_SOURCE
           Glibc 2.19 and earlier:
               _BSD_SOURCE

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Описание (Description)

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.

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Версии (Versions)

Since glibc version 2.32, the declarations of sys_errlist and
       sys_nerr are no longer exposed by <stdio.h>.

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Атрибуты (Attributes)

For an explanation of the terms used in this section, see
       attributes(7).

       ┌──────────────────────────┬───────────────┬─────────────────────┐
       │Interface                 │ Attribute     │ Value               │
       ├──────────────────────────┼───────────────┼─────────────────────┤
       │perror()                  │ Thread safety │ MT-Safe race:stderr │
       └──────────────────────────┴───────────────┴─────────────────────┘

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Стандарты (Conforming to)

perror(), errno: POSIX.1-2001, POSIX.1-2008, C89, C99, 4.3BSD.

       The externals sys_nerr and sys_errlist derive from BSD, but are
       not specified in POSIX.1.

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Примечание (Note)

The externals sys_nerr and sys_errlist are defined by glibc, but
       in <stdio.h>.

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Смотри также (See also)

err(3), errno(3), error(3), strerror(3)

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