System2

System2 is a cross-platform c library that allows you to call shell commands, just like system but with the ability to provide input to stdin and capture the output from stdout and stderr.

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From: https://patorjk.com with Graceful font

Features

• Written in C99, and is ready to be used in C++ as well
• Cross-platform (POSIX and Windows)
• Command interaction with stdin, stdout, and stderr
• Blocking (sync) and non-blocking (async) version
• No dependencies (only standard C and system libraries). No longer need a heavy framework like boost or poco just to capture output from running a command.
• Header only library (source version available as well)
• UTF-8 support*
• CMake integration

* See Remarks for UTF-8 support

API Documentation

Just read the header file System2.h. Everything is documented there.

Minimum running example (Without checks)

#include "System2.h"
#include <stdio.h>

int main(int argc, char** argv) 
{
    System2CommandInfo commandInfo;

    #if defined(__unix__) || defined(__APPLE__)
        System2Run("read testVar && echo testVar is \\\"$testVar\\\"", &commandInfo);
    #endif
    
    #if defined(_WIN32)
        System2Run( "set /p testVar= && echo testVar is \"!testVar!\"", 
                    &commandInfo);
    #endif
    
    char input[] = "test content\n";
    System2WriteToInput(&commandInfo, input, sizeof(input));
    
    //Waiting here simulates the child process has "finished" and we read the output of it
    //Sleep(2000);
    
    char outputBuffer[1024];
    uint32_t bytesRead = 0;
    
    //System2ReadFromOutput can also return SYSTEM2_RESULT_READ_NOT_FINISHED if we have more to read
    //In which case can use a do while loop to keep getting the output
    System2ReadFromOutput(&commandInfo, outputBuffer, 1023, &bytesRead);
    outputBuffer[bytesRead] = 0;
    
    int returnCode;
    System2GetCommandReturnValueSync(&commandInfo, &returnCode);
    
    printf("%s: %d\n", "Command has executed with return value", returnCode);
    printf("%s\n", outputBuffer);
    return 0;
    
    //Output: Command has executed with return value: 0
    //Output: testVar is "test content"
}

Using System2 in your project

This library has header only version, just include "System2.h" and you are good to go.

However, this will leak system library headers to your codebase as it uses it.

In that case, you can use the source version of the library.

1. Define SYSTEM2_DECLARATION_ONLY 1 before including System2.h

2. Then, either:

   • Add System2.c to you codebase
   • Or include System2.h in a single c file and define SYSTEM2_IMPLEMENTATION_ONLY 1 before it
   • Or link your project with System2 target in CMake`

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Remarks

• For POSIX, UTF-8 support should work if it is available on the system. This is however not tested.
• For Windows, UTF-8 support works for the command input (in theory XP and above but tested on Windows 10). However, the output part is NOT in UTF-8. The closest thing you can get for the output is UTF-16 as far as I know. Here's what needed to get output in UTF-16:
  1. Instead of System2Run("<your command>", &commandInfo), do System2Run("cmd /u /s /v /c \"<your command>\"", &commandInfo) This will output a UTF-16 string from cmd stdout/stderr
  2. Read output as usual from System2ReadFromOutput but interpret the output as wchar_t string instead.
     • You can then use WideCharToMultiByte to convert the output to UTF-8 if needed
  3. If you want to output the UTF-16 output to console, you need to use _setmode before calling wprintf/printf
     • See this for _setmode example