Last active
February 16, 2024 00:41
-
-
Save emanuele6/3f7e6a09af612fada3874b96e0a70475 to your computer and use it in GitHub Desktop.
chainif -- maintained version available at https://github.com/emanuele6/emanutils
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| #include <errno.h> | |
| #include <stdbool.h> | |
| #include <stdio.h> | |
| #include <spawn.h> | |
| #include <sys/wait.h> | |
| #include <unistd.h> | |
| extern char **environ; | |
| static char ** | |
| getblock(char *args[]) | |
| { | |
| if (!*args) | |
| return NULL; | |
| if (!**args) { | |
| *args = NULL; | |
| return &args[1]; | |
| } | |
| if (**args != ' ') | |
| return NULL; | |
| ++*args; | |
| return getblock(&args[1]); | |
| } | |
| static void | |
| usage() | |
| { | |
| static char const message[] = | |
| "Usage: chainif { condition... } { chain... } cmd...\n"; | |
| if (fputs(message, stderr) == EOF) | |
| perror("fputs"); | |
| } | |
| int | |
| main(int const argc, char *argv[]) | |
| { | |
| (void)argc; | |
| char **const condition = &argv[1]; | |
| char **const chain = getblock(condition); | |
| if (!chain) { | |
| usage(); | |
| return 2; | |
| } | |
| char **const cmd = getblock(chain); | |
| if (!cmd) { | |
| usage(); | |
| return 2; | |
| } | |
| bool dochain = *condition == NULL; | |
| if (!dochain) { | |
| pid_t pid; | |
| int const ret = posix_spawnp(&pid, *condition, NULL, NULL, | |
| condition, environ); | |
| if (ret) { | |
| perror("posix_spawnp"); | |
| return 2; | |
| } | |
| int status; | |
| for (;;) { | |
| int const ret = waitpid(pid, &status, 0); | |
| if (ret != -1) | |
| break; | |
| if (errno != EINTR) { | |
| perror("waitpid"); | |
| return 2; | |
| } | |
| } | |
| dochain = WIFEXITED(status) && WEXITSTATUS(status) == 0; | |
| } | |
| char **toexec; | |
| if (dochain) { | |
| toexec = &chain[1]; | |
| for (char **a = &cmd[-1]; a > chain; --a) | |
| *a = a[-1]; | |
| } else { | |
| toexec = cmd; | |
| } | |
| if (!*toexec) | |
| return 0; | |
| (void)execvp(*toexec, toexec); | |
| perror("execvp"); | |
| return 2; | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment