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#include "stddef.h" // for NULL
#include <__stdio.h> // for __FILE
#include <errno.h> // for EINVAL, errno
#include <fcntl.h> // for O_RDONLY, O_CLOEXEC, O_WRONLY
#include <stdio.h> // for FILE, fclose, fdopen, popen
#include <unistd.h> // for close, dup2, _exit, execl, fork, pipe2, STDIN_F...
FILE *popen(const char *command, const char *mode)
{
FILE *stream;
int oflag;
int pipefd[2];
switch (*mode) {
case 'r':
oflag = O_RDONLY;
break;
case 'w':
oflag = O_WRONLY;
break;
default:
errno = EINVAL;
return NULL;
}
if (pipe2(pipefd, O_CLOEXEC) < 0)
return NULL;
stream = fdopen(pipefd[oflag], mode);
if (stream == NULL) {
close(pipefd[0]);
close(pipefd[1]);
return NULL;
}
pid_t pid = fork();
if (pid < 0) {
close(pipefd[0]);
close(pipefd[1]);
fclose(stream);
return NULL;
}
if (pid == 0) {
if (oflag == O_RDONLY) {
dup2(pipefd[1], STDOUT_FILENO);
close(pipefd[0]);
close(pipefd[1]);
} else {
dup2(pipefd[0], STDIN_FILENO);
close(pipefd[0]);
close(pipefd[1]);
}
execl("/bin/sh", "sh", "-c", command, (char *)0);
_exit(127);
} else {
if (oflag == O_RDONLY) {
close(pipefd[1]);
} else {
close(pipefd[0]);
}
stream->pid = pid;
return stream;
}
}
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