system(S)                      6 January 1993                      system(S)


 Name

    system - issue a shell command

 Syntax


    cc  . . .  -lc


    #include  <stdio.h>
    #include  <stdlib.h>

    int system (string)
    char *string;


 Description

    The system function causes the string to be given to sh(C) as input, as
    if the string had been typed as a command at a terminal.  The current
    process waits until the shell has completed.

 Files

    /bin/sh

 Return value

    If string is not a null pointer, system returns the exit status of the
    shell in the same format as specified by the waitpid(S) function.  The
    meaning of the return value, if it is not -1, can be decoded via macros
    like WIFEXITED defined in <sys/wait.h>, as described in waitpid(S).

 Diagnostics

    The system function forks to create a child process that in turn executes
    (using exec(S)) /bin/sh in order to execute string.  If the fork fails,
    system returns -1 and sets errno.  If the fork succeeds but exec fails,
    system returns a value as if sh(C) had terminated using exit(127).

    The system function fails if:

    [EAGAIN]       The system-imposed limit on the total number of processes
                   under execution, system-wide, or by a single user ID
                   (CHILDMAX), would be exceeded.

    [ENOMEM]       Insufficient storage space is available.


 See also

    exec(S), sh(C)

 Standards conformance

    system is conformant with:
    AT&T SVID Issue 2;
    X/Open Portability Guide, Issue 3, 1989;
    and ANSI X3.159-1989 Programming Language -- C.