141 lines
3.0 KiB
C
Executable File
141 lines
3.0 KiB
C
Executable File
#define _POSIX_C_SOURCE 200809L
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/wait.h>
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#include <signal.h>
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#include <libgen.h>
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#include <errno.h>
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#include <limits.h>
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#define ARG_SEP " " /* Argument separator for commands */
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#define PROMPT " $ "
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char** create_argv(char* command);
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int get_argc(char* command);
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char* prompt();
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int cd(char* path);
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int main() {
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char** argv;
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char* user_input;
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pid_t child_pid;
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int stat_loc; /* ??? (Needed for waitpid) */
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signal(SIGINT, SIG_IGN);
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while(1) {
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user_input = prompt();
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argv = create_argv(user_input);
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if(strcmp(argv[0], "cd") == 0) {
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if(cd(argv[1]) < 0) {
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perror(argv[1]);
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}
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/* causes the fork to get skipped */
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continue;
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}
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else if(strcmp(argv[0], "exit") == 0 ||
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strcmp(argv[0], "quit") == 0) {
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exit(0);
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}
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child_pid = fork();
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if(child_pid < 0) {
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/* Could not start child process. Check why and error out. */
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if(errno == EAGAIN) {
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perror("Could not execute command: insufficient resources");
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exit(1);
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}
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else if(errno == ENOMEM) {
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/* Is this out of RAM or out of storage? */
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perror("Could not execute command: insufficient storage space");
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exit(1);
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}
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else {
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perror("Could not execute command: unknown failure");
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exit(1);
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}
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}
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else if(child_pid == 0) {
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/* We are the child, so allow ^C */
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signal(SIGINT, SIG_DFL);
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if(execvp(argv[0], argv) < 0) {
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perror(argv[0]);
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exit(1);
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}
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}
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else {
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/* Wait for the child to finish */
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waitpid(child_pid, &stat_loc, WUNTRACED);
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}
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free(user_input);
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free(argv);
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}
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return 0;
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}
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char** create_argv(char* command) {
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int argc = get_argc(command) + 1;
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char* temp;
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int i = 0;
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char** argv = calloc(argc, sizeof(*argv));
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if(argv == NULL) {
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perror("Unable to parse command: could not allocate memory");
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exit(1);
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}
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for(temp = strtok(command, ARG_SEP); temp != NULL;
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temp = strtok(NULL, ARG_SEP)) {
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argv[i] = temp;
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i++;
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}
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/* Set last item in argv to NULL, since execvp requires it */
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argv[i] = NULL;
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return argv;
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}
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char* prompt() {
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char cwd[PATH_MAX];
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getcwd(cwd, sizeof(cwd));
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char* bname = basename(cwd);
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char prompt[PATH_MAX + 5] = "";
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strcat(prompt, bname);
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strcat(prompt, PROMPT);
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char* input = calloc(LINE_MAX, sizeof(*input));
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if(input == NULL) {
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perror("Unable to read command: could not allocate memory");
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exit(1);
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}
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printf("%s", prompt);
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fgets(input, LINE_MAX, stdin);
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input[strcspn(input, "\r\n")] = '\0';
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return input;
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}
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int get_argc(char* command) {
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int argc = 0, word = 0;
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char* command_iter = command;
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do {
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switch(*command_iter) {
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case '\0':
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case ' ':
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case '\t': if(word) { word = 0; argc++; }
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default: word = 1;
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}
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} while(*(command_iter++));
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return argc;
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}
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int cd(char* path) {
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return chdir(path);
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}
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