perror(S)                      6 January 1993                      perror(S)


 Name

    perror - system error messages

 Syntax


    cc  . . .  -lc


    void perror (s)
    const char *s;

    extern int errno;

    extern char *sys_errlist[];

    extern int sys_nerr;


 Description

    The perror function produces a message on the standard error output,
    describing the last error encountered during a call to a system or
    library function.  The argument string s is printed first, then a colon
    and a blank, then the message and a new-line.  (However, if s=" ", the
    colon is not printed.)  To be of most use, the argument string should
    include the name of the program that incurred the error.  The error num-
    ber is taken from the external variable errno, which is set when errors
    occur but not cleared when non-erroneous calls are made.

    To simplify variant formatting of messages, the array of message strings
    syserrlist is provided; errno can be used as an index into this table to
    get the message string without the new-line.  sysnerr is the number of
    messages in the table; it should be checked because new error codes may
    be added to the system before they are added to the table.

 See also

    Intro(S)

 Standards conformance

    errno is conformant with:
    AT&T SVID Issue 2;
    X/Open Portability Guide, Issue 3, 1989;
    Intel386 Binary Compatibility Specification, Edition 2 (iBCSe2);
    IEEE POSIX Std 1003.1-1990 System Application Program Interface (API) [C
    Language] (ISO/IEC 9945-1);
    and NIST FIPS 151-1.

    perror is conformant with:
    AT&T SVID Issue 2;
    X/Open Portability Guide, Issue 3, 1989;
    ANSI X3.159-1989 Programming Language -- C;
    IEEE POSIX Std 1003.1-1990 System Application Program Interface (API) [C
    Language] (ISO/IEC 9945-1);
    and NIST FIPS 151-1.

    syserrlist and sysnerr are conformant with:
    AT&T SVID Issue 2; however, syserrlist and sysnerr have been withdrawn
    from XPG3.