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    cpp/utility/program/system: Difference between revisions

    From cppreference.com
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    +popen in notes
    m s/NULL/null, and made the example output that file it created
    Line 2: Line 2:
    {{cpp/utility/program/navbar}}
    {{cpp/utility/program/navbar}}
    {{ddcl | header=cstdlib |
    {{ddcl | header=cstdlib |
    int system( const char *command );
    int system( const char* command );
    }}
    }}


    Calls the host environment's command processor with command parameter. Returns implementation-defined value (usually the value that the invoked program returns).
    Calls the host environment's command processor with command. Returns implementation-defined value (usually the value that the invoked program returns).


    If command is the {{lc|NULL}} pointer, checks if host environment has a command processor and returns nonzero value only if the command processor exists.
    If {{|}} pointer, checks if host environment has a command processor and returns nonzero value only if the command processor exists.


    ===Parameters===
    ===Parameters===
    {{par begin}}
    {{par begin}}
    {{par | command | character string identifying the command to be run in the command processor. If 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 pointer is given, command processor is checked for existence}}
    {{par end}}
    {{par end}}


    ===Return value===
    ===Return value===
    Implementation-defined value. If {{tt|command}} is {{lc|NULL}} returns nonzero value only if command processor exists.
    Implementation-defined value. If {{tt|command}} is returns nonzero value only if command processor exists.


    ===Notes===
    ===Notes===
    Line 21: Line 21:


    ===Example===
    ===Example===
    In this example there is a system call of the unix command '''ls -l >test.txt''':
    {{example
    {{example
      |
      |
      | code=
      | code=
    #include <cstdlib>
    #include <cstdlib>


    int main()
    int main()
    {
    {
         std::system("ls -l >test.txt");
         std::system("ls -l >test.txt"
    );
    }
    }
      | output=
      | output=
    }}
    }}


    Revision as of 20:56, 30 September 2015

     
    C++
     
    Utilities library
    General utilities
    Relational operators (deprecated in C++20)
     
    Program support utilities
     
    Defined in header <cstdlib> 
    int system( const char* command );

    Calls the host environment's command processor (/bin/sh, cmd.exe, command.com) 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 host environment has a command processor and returns nonzero value 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 nonzero value only if command processor exists.

    Notes

    Related POSIX function popen makes the output generated by command available to the caller.

    Example

    Run this code
    #include <cstdlib>
#include <fstream>
#include <iostream>

int main()
{
    std::system("ls -l >test.txt"); // execute 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