Aprz Shell

Question

Well, ever since I switched to Linux, I've been interested in os development. An important part of the operating system is the shell. So recently, I decided to write my own shell, which I hope I can make featureful and robust enough to use in place of GNU Bash.
I am not so sure if this is the appropriate forum because it could work in Community Contribution too in my opinion and this isn't a programming question really, just sharing the source code, but you guys can criticize and suggest things.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
char *args[80];
char input[80];
int errno;
int i;
int main(void) {
while(strcmp(input, "exit")) {
i = 1;
do {
printf("Aprz-0.3$ ");
gets(input);
} while(input[0] == '\0');
args[0] = strtok(input, " ");
while((args[i] = strtok(NULL, " ")) != NULL && ++i);
if(!strcmp(args[0], "cd")) {
chdir(args[1]);
continue;
if(fork() == 0 && strcmp(input, "exit")) {
errno = execvp(args[0], args);
if(errno < 0) printf("%s: command not found!\n", args[0]);
exit(1);
} else wait(NULL);
return 0;
This is version 0.3 of it. I've been sharing this with other people on two private forums, but they haven't been so enthusiastic as I am about it so I figured putting it in a public spot such as this full of technical experts and enthusiast will get me better input.
I am terribly sorry I haven't commented it either, haha! I meant to do that starting from day 1, but I slacked off on that instead since it's so small.
Oh, feel free to distribute, modify, and all that nonsense. Don't forget to give me credit though. Also please, if you're taking an operating system class and you're suppose to make a shell, don't cheat yourself and the class by using this.
I am mostly making this just for kicks, but I am also giving it a lot of attention right now.
Anyhow, criticism, questions, and suggestion will be greatly appreciated.
Last edited by Aprz (2009-04-15 02:19:57)

Answer 1

Heh, not so sure if it is a good template, but I guess all software, good or bad, should be free.
Edit: Current progress of Aprz-0.4. I actually took the seconds to annotate the code. I also added put putenv() so I wouldn't have to type /sbin/reboot and stuff like that. So you may want to edit it.
-code removed to keep post size small-
I hope by annotation the source code and putting envp() at line 48. This will make it easier to use and edit. I actually don't know how to pipe yet, but I am going to look at it soon. I hear it is easy.
Edit: Removed the code above with some very minor errors and posting it here. XD
/* Aprz Shell - an interactive prompt that execute commands
* Feel free to modify this however you wish, change it, redistribute it,
* blah blah blah, just as long as you give me credit for starting
* this mini project off. School childern shall not turn this in as
* their homework assignment by the way (even though I doubt this is
* even considered near a C+ right. What do you guys give this? A D-
* right now since there is no tab completion? :(
* If you notice any mistake in documentation in the source code, any
* minor (or major) programming errors, have a suggestion, or anything
* like that, feel free to notify me.
* Name is Andrew Przepioski.
* E-mail: [email protected]
* ========================================================================
* !!! IMPORTANT !!! IMPORTANT !!! IMPORTANT !!! IMPORTANT !!! IMPORTANT !!!
* =========================================================================
* Did I get your attention now? Yes at line 48, you need to edit it
* to fit you... I am just going to leave it as the default in
* in the source code and it is up to you to edit it! It is your
* PATH.
* THANKS
* Ventrue - Pointed out a few typos and grammatical errors.
* Milo - Pointed out that PATH doesnt need ':' at the end of it.
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
/* args - my imitation of argv
* input - the user's input
* argc - my imitation of argc
* ret - return*/
char *args[128];
char input[128];
int argc;
int ret;
/* Isn't the name and what it is doing obvious enough?! Gosh... */
void sighandler(int signo) {
write(1, "\r", 1);
int main(void) {
/* Set PATH or else it would just be "/bin:/usr/bin:". */
putenv("PATH=/bin:/usr/bin");
/* If you're using firefox and have fancy things like flash,
* you'll want this. */
/*putenv("MOZ_PLUGIN_PATH=/usr/lib/mozilla/plugins:/opt/mozilla/lib/plugins");*/
/* Disable ctrl-c. This also disabled ctrl-d and other guys,
* I'll work on that later since I am feeling lazy. */
signal(SIGINT, SIG_IGN);
signal(SIGINT, sighandler);
/* Nice going Captain Obvious.. ;) Yes, this is the loop
* that keeps Aprz Shell alive until the user enters exit. */
while(strcmp(input, "exit")) {
/* argc 0 would be the program name. */
argc = 1;
/* Print out a lovely prompt and let the user type
* in junk. */
do {
printf("Aprz-0.4$ ");
fgets(input, 128, stdin);
} while(input[0] == '\0');
/* Fix a minor detail with using fgets(). */
input[strlen(input) - 1] = '\0';
/* Parse/tokenize the user's input using space as
* a delimiter. */
args[0] = strtok(input, " ");
while((args[argc] = strtok(NULL, " ")) != NULL && ++argc);
/* Magically change directories. */
if(!strcmp(args[0], "cd")) {
chdir(args[1]);
continue;
/* Initiate process and execute the user input. */
if(!fork()) {
ret = execvp(args[0], args);
if(ret < 0 && strcmp(input, "exit")) printf("%s: command not found!\n", args[0]);
exit(0);
} else wait(NULL);
return 0;
Edit: Hm... I think I'll need to do something like #define to set PATH. Seems like a pain to scroll down to edit that and edit me saying where it is at ^ cause it's not in the right spot anymore.
Last edited by Aprz (2009-04-17 22:47:36)