system.3

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)system.3	6.3	8/30/89
.TH system 3
.SH Name
system \- issue a shell command 
.SH Syntax
.nf
.B system(\fIstring\fP)
.B char *\fIstring\fP;
.fi
.SH Description
.NXR "system subroutine (standard C)"
.NXR "shell command" "issuing"
If the
.I string
argument is the NULL pointer (0) the
.PN system
function tests the accessibility of
the command interpreter
.MS sh 1 .
The function will return zero for failure to find the command
interpreter, and positive if successful.
.PP
If the
.I string
argument is non-NULL the
.PN system
routine causes the
.I string
to be given to 
.MS sh 1
as input as if the string had been typed as a command
at a terminal.
The current process waits until the shell has
completed, then returns the exit status in the form that
.MS wait 2
returns.
.SH Diagnostics
Exit status 127 indicates the shell couldn't be executed.
.SH See Also
execve(2), wait(2), popen(3)