cpp/utility/program/system: Difference between revisions
From cppreference.com
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{{cpp/title| system}} | {{cpp/title|system}} | ||
{{cpp/utility/program/navbar}} | {{cpp/utility/program/navbar}} | ||
{{ddcl | header=cstdlib | | {{ddcl|header=cstdlib| | ||
int system( const char* command ); | int system( const char* command ); | ||
}} | }} | ||
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===Parameters=== | ===Parameters=== | ||
{{par begin}} | {{par begin}} | ||
{{par | command | character string identifying the command to be run in the command processor. If a null pointer is given, command processor is checked for existence}} | {{par|command|character string identifying the command to be run in the command processor. If a null pointer is given, command processor is checked for existence}} | ||
{{par end}} | {{par end}} | ||
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===Notes=== | ===Notes=== | ||
On POSIX systems, the return value can be decomposed using [ | On POSIX systems, the return value can be decomposed using [://pubs.opengroup.org/onlinepubs/9699919799/functions/wait.html WEXITSTATUSand WSTOPSIG] | ||
The related POSIX function [ | The related POSIX function [://pubs.opengroup.org/onlinepubs/9699919799/functions/popen.html popen] makes the output generated by {{tt|command}} available to the caller. | ||
An explicit flush of {{lc|std::cout}} is also necessary before a call to {{lc|std::system}}, if the spawned process performs any screen I/O. | An explicit flush of {{lc|std::cout}} is also necessary before a call to {{lc|std::system}}, if the spawned process performs any screen I/O. | ||
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===Example=== | ===Example=== | ||
{{example | {{example | ||
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|code= | |||
#include <cstdlib> | #include <cstdlib> | ||
#include <fstream> | #include <fstream> | ||
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int main() | int main() | ||
{ | { | ||
std::system("ls -l >test.txt"); // | std::system("ls -l >test.txt"); // the UNIX command "ls -l >test.txt" | ||
std::cout << std::ifstream("test.txt").rdbuf(); | std::cout << std::ifstream("test.txt").rdbuf(); | ||
} | } | ||
|p=true | |p=true | ||
|output= | |||
total 16 | total 16 | ||
-rwxr-xr-x 1 2001 2000 8859 Sep 30 20:52 a.out | -rwxr-xr-x 1 2001 2000 8859 Sep 30 20:52 a.out | ||
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===See also=== | ===See also=== | ||
{{dsc begin}} | {{dsc begin}} | ||
{{dsc see c | c/program/system}} | {{dsc see c|c/program/system}} | ||
{{dsc end}} | {{dsc end}} | ||
{{langlinks|de|es|fr|it|ja|pt|ru|zh}} | {{langlinks|de|es|fr|it|ja|pt|ru|zh}} | ||
Latest revision as of 23:38, 30 March 2023
| Defined in header <cstdlib>
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int system( const char* command );
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Calls the host environment's command processor (e.g. /bin/sh, cmd.exe) with the parameter command. Returns an implementation-defined value (usually the value that the invoked program returns).
If command is a null pointer, checks if the host environment has a command processor and returns a nonzero value if and only if the command processor exists.
Parameters
| command | - | character string identifying the command to be run in the command processor. If a null pointer is given, command processor is checked for existence |
Return value
Implementation-defined value. If command is a null pointer, returns a nonzero value if and only if the command processor exists.
Notes
On POSIX systems, the return value can be decomposed using WEXITSTATUS and WSTOPSIG.
The related POSIX function popen makes the output generated by command available to the caller.
An explicit flush of std::cout is also necessary before a call to std::system, if the spawned process performs any screen I/O.
Example
Run this code
#include <cstdlib>
#include <fstream>
#include <iostream>
int main()
{
std::system("ls -l >test.txt"); // executes the UNIX command "ls -l >test.txt"
std::cout << std::ifstream("test.txt").rdbuf();
}
Possible output:
total 16
-rwxr-xr-x 1 2001 2000 8859 Sep 30 20:52 a.out
-rw-rw-rw- 1 2001 2000 161 Sep 30 20:52 main.cpp
-rw-r--r-- 1 2001 2000 0 Sep 30 20:52 test.txt
See also
C documentation for system
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