catsh stands for C As Tangled SHell script.
A tiny C library to execute shell commands with input/output redirection, implemented in pure C.
As I like to use C, and for now I don't want to learn any other language, so I made this. At least C is more strict than shell script, that means less bugs (I hope so).
Simple, stupid, paranoid, but I like it.
It's part of the low-level implemention of rurima.
This library is STILL WIP, but since 0.6.0, struct cth_result and related functions are ABI stable.
However, non-blocking process execution is NOT YET supported.
#include "include/catsh.h" int main(void) { char *stdin_msg = "Hello, catsh from stdin!\n"; struct cth_result *res = cth_exec((char *[]){ "sh", "-c", "cat;echo Hello, catsh from stdout!; echo Hello, catsh from stderr! >&2; exit 0", NULL }, stdin_msg, true, true); printf("Demo: Execute a shell command with input and capture output\n"); if (CTH_EXEC_SUCCEED(res)) { printf(" exit code = %d\n", res->exit_code); printf(" stdin(input):\n%s", stdin_msg); if (res->stdout_ret) printf(" stdout:\n%s", res->stdout_ret); else printf(" stdout: (null)\n"); if (res->stderr_ret) printf(" stderr:\n%s", res->stderr_ret); else printf(" stderr: (null)\n"); cth_free_result(&res); } else { if (CTH_EXEC_FAILED(res)) { printf(" Command exited with code %d\n", res->exit_code); cth_free_result(&res); } else if (CTH_EXEC_RUNNING(res)) { printf(" Command is still running\n"); cth_free_result(&res); } else if (CTH_EXEC_CANNOT_RUN(res)) { printf(" Cannot run command\n"); } } return 0; }
Results:
Demo: Execute a shell command with input and capture output
exit code = 0
stdin(input):
Hello, catsh from stdin!
stdout:
Hello, catsh from stdin!
Hello, catsh from stdout!
stderr:
Hello, catsh from stderr!
Not very scientific, just a simple test.
Tested on Ubuntu 24.04.3 LTS, OrbStack vm, MacBook Air M4.
Performance Test: 128MB random string
Command: cat
Symmetric output: output equals input
Average elapsed time for 'cth_exec()': 0.030548 seconds
Average elapsed time for 'sh -c "x=$(cat temp_input.txt)"': 0.225729 seconds
Used -638.93% more time than shell variable $()
Performance Test: 1000x 'ls' command
Command: ls >/dev/null (shell script vs cth_exec)
Average elapsed time for 1000x 'ls' in shell script: 0.236063 seconds
Average elapsed time for 1000x 'ls' via cth_exec(): 0.023837 seconds
Used -89.90% more time than shell script
Negative value means cth_exec() is faster.
I think this is a good result, as catsh is only for small tasks.