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system(3) [freebsd man page]

SYSTEM(3)						   BSD Library Functions Manual 						 SYSTEM(3)

NAME
system -- pass a command to the shell LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <stdlib.h> int system(const char *string); DESCRIPTION
The system() function hands the argument string to the command interpreter sh(1). The calling process waits for the shell to finish execut- ing the command, ignoring SIGINT and SIGQUIT, and blocking SIGCHLD. If string is a NULL pointer, system() will return non-zero if the command interpreter sh(1) is available, and zero if it is not. RETURN VALUES
The system() function returns the exit status of the shell as returned by waitpid(2), or -1 if an error occurred when invoking fork(2) or waitpid(2). A return value of 127 means the execution of the shell failed. SEE ALSO
sh(1), execve(2), fork(2), waitpid(2), popen(3) STANDARDS
The system() function conforms to ISO/IEC 9899:1990 (``ISO C90'') and is expected to be IEEE Std 1003.2 (``POSIX.2'') compatible. BSD
June 4, 1993 BSD

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system(3C)																system(3C)

NAME
system - issue a shell command SYNOPSIS
#include <stdlib.h> int system(const char *string); The system() function causes string to be given to the shell as input, as if string had been typed as a command at a terminal. The invoker waits until the shell has completed, then returns the exit status of the shell in the format specified by waitpid(3C). If string is a null pointer, system() checks if the shell exists and is executable. If the shell is available, system() returns a non-zero value; otherwise, it returns 0. The standard to which the caller conforms determines which shell is used. See standards(5). The system() function executes vfork(2) to create a child process that in turn invokes one of the exec family of functions (see exec(2)) on the shell to execute string. If vfork() or the exec function fails, system() returns -1 and sets errno to indicate the error. The system() function fails if: EAGAIN The system-imposed limit on the total number of processes under execution by a single user would be exceeded. EINTR The system() function was interrupted by a signal. ENOMEM The new process requires more memory than is available. USAGE
The system() function manipulates the signal handlers for SIGINT, SIGQUIT, and SIGCHLD. It is therefore not safe to call system() in a mul- tithreaded process, since some other thread that manipulates these signal handlers and a thread that concurrently calls system() can inter- fere with each other in a destructive manner. If, however, no such other thread is active, system() can safely be called concurrently from multiple threads. See popen(3C) for an alternative to system() that is thread-safe. See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |Unsafe | +-----------------------------+-----------------------------+ ksh(1), sh(1), exec(2), vfork(2), popen(3C), waitpid(3C), attributes(5), standards(5) 18 Dec 2003 system(3C)

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