It seems like there's no good library function I can use for popen with array of arguments instead of single shell-interpreted shell. So I implemented my own one: c h.
Here is the code:
popen_arr.h
#pragma once
struct FILE;
// Implemented by Vitaly _Vi Shukela in 2013, License=MIT
/**
* Fork and exec the program, enabling stdio access to stdin and stdout of the program
* You may close opened streams with fclose.
* Note: the procedure does no signal handling except of signal(SIGPIPE, SIG_IGN);
* You should waitpid for the returned PID to collect the zombie or use signal(SIGCHLD, SIG_IGN);
*
* @arg in stdin of the program, to be written to. If NULL then not redirected
* @arg out stdout of the program, to be read from. If NULL then not redirected
* @arg program full path of the program, without reference to $PATH
* @arg argv NULL terminated array of strings, program arguments (includiong program name)
* @arg envp NULL terminated array of environment variables, NULL => preserve environment
* @return PID of the program or -1 if failed
*/
int popen2_arr (FILE** in, FILE** out, const char* program, const char* const argv[], const char* const envp[]);
/** like popen2_arr, but uses execvp/execvpe instead of execve/execv, so looks up $PATH */
int popen2_arr_p(FILE** in, FILE** out, const char* program, const char* const argv[], const char* const envp[]);
/**
* Simplified interface to popen2_arr.
* You may close the returned stream with fclose.
* Note: the procedure does no signal handling except of signal(SIGPIPE, SIG_IGN);
* You should wait(2) after closing the descriptor to collect zombie process or use signal(SIGCHLD, SIG_IGN)
*
* @arg program program name, can rely on $PATH
* @arg argv program arguments, NULL-terminated const char* array
* @arg pipe_into_program 1 to be like popen(...,"w"), 0 to be like popen(...,"r")
* @return FILE* instance or NULL if error
*/
FILE* popen_arr(const char* program, const char* const argv[], int pipe_into_program);
popen_arr.c
#define _GNU_SOURCE // execvpe
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include "popen_arr.h"
// Implemented by Vitaly _Vi Shukela in 2013, License=MIT
static int popen2_impl(FILE** in, FILE** out, const char* program, const char* const argv[], const char* const envp[], int lookup_path) {
int child_stdout = -1;
int child_stdin = -1;
int to_be_written = -1;
int to_be_read = -1;
if(in) {
int p[2]={-1,-1};
int ret = pipe(p);
if(ret!=0) { return -1; }
to_be_written=p[1];
child_stdin =p[0];
*in = fdopen(to_be_written, "w");
if (*in == NULL) {
close(to_be_written);
close(child_stdin);
return -1;
}
}
if(out) {
int p[2]={-1,-1};
int ret = pipe(p);
if(ret!=0) {
if (in) {
close(child_stdin);
fclose(*in);
*in = NULL;
}
return -1;
}
to_be_read =p[0];
child_stdout=p[1];
*out = fdopen(to_be_read, "r");
}
int childpid = fork();
if(!childpid) {
if(child_stdout!=-1) {
close(to_be_read);
dup2(child_stdout, 1);
close(child_stdout);
}
if(child_stdin!=-1) {
close(to_be_written);
dup2(child_stdin, 0);
close(child_stdin);
}
if (lookup_path) {
if (envp) {
execvpe(program, (char**)argv, (char**)envp);
} else {
execvp (program, (char**)argv);
}
} else {
if (envp) {
execve(program, (char**)argv, (char**)envp);
} else {
execv (program, (char**)argv);
}
}
_exit(ENOSYS);
}
if(child_stdout!=-1) {
close(child_stdout);
}
if(child_stdin!=-1) {
close(child_stdin);
}
return childpid;
}
int popen2_arr (FILE** in, FILE** out, const char* program, const char* const argv[], const char* const envp[])
{
signal(SIGPIPE, SIG_IGN);
return popen2_impl(in, out, program, argv, envp, 0);
}
int popen2_arr_p(FILE** in, FILE** out, const char* program, const char* const argv[], const char* const envp[])
{
signal(SIGPIPE, SIG_IGN);
return popen2_impl(in, out, program, argv, envp, 1);
}
FILE* popen_arr(const char* program, const char* const argv[], int pipe_into_program) {
FILE* f = NULL;
if (pipe_into_program) {
popen2_arr_p(&f, NULL, program, argv, NULL);
} else {
popen2_arr_p(NULL, &f, program, argv, NULL);
}
return f;
}
Do you have any advices how to promote it from just a project's code snippet into a reusable little library? Is API good? Shall it provide more features (at expence of being complexier) or more simpler (but a bit tricker to use)? Are there obviously bad parts of the code?
