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system(3) [osf1 man page]

system(3)						     Library Functions Manual							 system(3)

NAME
system - Executes a shell command LIBRARY
Standard C Library (libc.so, libc.a) SYNOPSIS
#include <stdlib.h> int system( const char *string); STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: system(): XPG4, XPG4-UNIX Refer to the standards(5) reference page for more information about industry standards and associated tags. PARAMETERS
Specifies a valid sh shell command. If string is NULL (0), the system() function tests the accessibility of the sh command interpreter. If string is not NULL, the system() function passes the parameter to the sh command, which interprets string as a command and exe- cutes it. DESCRIPTION
The system() function passes the string parameter to the sh command, which interprets string as a command and executes it. The system() function invokes the fork() function to create a child process that in turn uses the exec function to run sh, which interprets the shell command contained in the string parameter. The current process waits until the shell has completed before returning. RETURN VALUES
If the string parameter is NULL, the system() function returns 0 if it is unable to access the command interpreter or a non-zero value if sh is accessible. If the string parameter is not NULL, upon successful completion by sh, the system() function returns the exit status of the shell process in the form that wait(2) returns. Otherwise, the system() function returns a value of -1 and sets errno to indicate the error. Exit status 127 indicates that the shell could not be executed. Note that the exit status should only be interpreted using the macros described in wait(2) and defined in the sys/wait.h header file. ERRORS
The system() function sets errno to the specified values for the following conditions: The status of the child process created by system() is no longer available. In addition, the system() function may set errno values as described by fork(). RELATED INFORMATION
Functions: exec(2), exit(2), fork(2), wait(2) Commands: sh(1) Standards: standards(5) delim off system(3)

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system(3S)																system(3S)

NAME
system() - issue a shell command SYNOPSIS
DESCRIPTION
executes the command specified by the string pointed to by command. The environment of the executed command is as if a child process were created using (see fork(2)), and the child process invoked the sh-posix(1) utility via a call to (see exec(2)) as follows: ignores the and signals, and blocks the signal, while waiting for the command to terminate. If this might cause the application to miss a signal that would have killed it, the application should examine the return value from and take whatever action is appropriate to the application if the command terminated due to receipt of a signal. does not affect the termination status of any child of the calling processes other than the process or processes it itself creates. does not return until the child process has terminated. APPLICATION USAGE
If the return value of is not -1, its value can be decoded through the use of the macros described in For convenience, these macros are also provided in Note that, while must ignore and and block while waiting for the child to terminate, the handling of signals in the executed command is as specified by fork(2) and exec(2). For example, if is being caught or is set to when is called, the child is started with handling set to Ignoring and in the parent process prevents coordination problems (such as two processes reading from the same terminal) when the executed command ignores or catches one of the signals. RETURN VALUE
If command is null, returns non-zero. If command is not null, returns the termination status of the command language interpreter in the format specified by wait(2). The termi- nation status of the command language interpreter is as specified for sh-posix(1), except that if some error prevents the command language interpreter from executing after the child process is created, the return value from is as if the command language interpreter had termi- nated using If a child process cannot be created, or if the termination status for the command language interpreter cannot be obtained, returns -1 and sets to indicate the error. DIAGNOSTICS
forks to create a child process which, in turn, in order to execute string. If the fork fails, returns -1 and sets If the exec fails, returns the status value returned by (see wait(2)) for a process that terminates with a call of ERRORS
If errors are encountered, sets values as described by fork(2). FILES
SEE ALSO
sh(1), fork(2), exec(2), wait(2), thread_safety(5). STANDARDS CONFORMANCE
system(3S)

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