🐜 subprocess.h

A simple one header solution to launching processes and interacting with them for C/C++.

Usage

Just #include "subprocess.h" in your code!

The current supported compilers are gcc, clang and msvc.

The current supported platforms are Linux, macOS and Windows.

Design

Subprocess is a single header cross-platform library that allows users to launch sub-processes, interact with the stdin, stdout, and stderr of the process, and wait for them to complete.

Launching a Process

To launch a process you call subprocess_create like so:

const char *command_line[] = {"echo", "\"Hello, world!\"", NULL};
struct subprocess_s subprocess;
int result = subprocess_create(command_line, 0, &subprocess);
if (0 != result) {
  // an error occurred!
}

You specify an array of string for the command line - terminating the array with a NULL element.

If the process is created successfully then 0 is returned from subprocess_create.

Writing to the Standard Input of a Process

To write to the standard input of a child process you call subprocess_stdin to get the FILE handle to write with, passing a previously created process, like so:

FILE* p_stdin = subprocess_stdin(&process);
fputs("Hello, world!", p_stdin);

Care must be taken to not write to the stdin after any call to subprocess_join or subprocess_destroy.

Reading from the Standard Output of a Process

To read from the standard output of a child process you call subprocess_stdout to get the FILE handle to read with, passing a previously created process, like so:

FILE* p_stdout = subprocess_stdout(&process);
char hello_world[32];
fgets(hello_world, 32, p_stdout);

Care must be taken to not read from the stdout after any call to subprocess_destroy.

Reading from the Standard Error of a Process

To read from the standard error of a child process you call subprocess_stderr to get the FILE handle to read with, passing a previously created process, like so:

FILE* p_stderr = subprocess_stderr(&process);
char hello_world[32];
fgets(hello_world, 32, p_stderr);

Care must be taken to not read from the stderr after any call to subprocess_destroy.

Waiting on a Process

To wait for a previously created process to finish executing you call subprocess_join like so:

int process_return;
int result = subprocess_join(&process, &process_return);
if (0 != result) {
  // an error occurred!
}

The return code of the child process is returned in the second argument (stored into process_return in the example above). This parameter can be NULL if you don't care about the process' return code.

If the child process encounters an unhandled exception, the return code will always be filled with a non zero value.

Destroying a Process

To destroy a previously created process you call subprocess_destroy like so:

int result = subprocess_destroy(&process);
if (0 != result) {
  // an error occurred!
}

Note that you can destroy a process before it has completed execution - this allows you to spawn a process that would outlive the execution of the parent process for instance.

Terminating a Process

To terminate a (possibly hung) previously created process you call subprocess_terminate like so:

int result = subprocess_terminate(&process);
if (0 != result) {
  // an error occurred!
}

Note that you still can call subprocess_destroy, and subprocess_join after calling subprocess_terminate, and that the return code filled by subprocess_join(&process, &process_return) is then guaranted to be non zero.

Reading Asynchronously

If you want to be able to read from a process before calling subprocess_join on it, you cannot use subprocess_stdout or subprocess_stderr because the various operating systems that this library supports do not allow for this.

Instead you first have to call subprocess_create and specify the subprocess_option_enable_async option - which enables asynchronous reading.

Then you must use the subprocess_read_stdout and subprocess_read_stderr helper functions to do any reading from either pipe. Note that these calls may block if there isn't any data ready to be read.

Todo

The current list of todos:

Add the ability to set environment variables of the child process as suggested by @graphitemaster.
Add the ability to specify if a child process should die if the parent process is terminated.

License

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.

In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to http://unlicense.org/

yindian/subprocess.h