diff options
| -rw-r--r-- | Makefile | 5 | ||||
| -rw-r--r-- | shell.c | 157 | ||||
| -rw-r--r-- | shell.h | 8 |
3 files changed, 170 insertions, 0 deletions
diff --git a/Makefile b/Makefile new file mode 100644 index 0000000..120ce9d --- /dev/null +++ b/Makefile @@ -0,0 +1,5 @@ +./shell: shell.c + gcc shell.c -o ./shell + +clean: + rm -f ./shell @@ -0,0 +1,157 @@ +#include <sys/wait.h> +#include <stdio.h> +#include <stdlib.h> +#include <unistd.h> +#include <string.h> +#include <limits.h> +#include <stdbool.h> +#include "shell.h" + +#define MAX_CMD 1024 +#define MAX_PATH 512 + +int main(int argc, char* argv[]) { + // setup an array of the values in $PATH + char* pathstr = getenv("PATH"); + const char* delim = ":"; + const char* cmddelim = " "; + const int binlen = strcnt(pathstr, delim[0]) + 1; + char* bins[binlen]; + char* path = strtok(pathstr, delim); + int i = 0; + while (path != NULL) { + bins[i++] = path; + path = strtok(NULL, delim); + } + + while (true) { + //prefix command, show user, host, cwd + char hostbfr[256]; + gethostname(hostbfr, sizeof(hostbfr)); + char cwdbfr[MAX_PATH]; + getcwd(cwdbfr, sizeof(cwdbfr)); + printf( + "[\033[1;32m%s\033[0m@\033[1;31m%s\033[0m]:\033[1;34m%s\033[1;31m$ \033[0m", getenv("USER"), + hostbfr, cwdbfr + ); + + // get the input string - keep accepting words until a newline + char cmdstr[MAX_CMD]; + scanf("%[^\n]", cmdstr); + int c; + while ((c = getchar()) != '\n' && c != EOF); //clear buffer + + // parse the input string into an array, splitting by spaces + uint cmdlen = strcnt(cmdstr, cmddelim[0]) + 1; + char* cmdarr[cmdlen + 1]; + char* arg = strtok(cmdstr, cmddelim); + i = 0; + while (arg != NULL) { + cmdarr[i++] = arg; + arg = strtok(NULL, cmddelim); + } + + //work out if we need to change the cwd + if (strcmp(cmdarr[0], "cd") == 0) { + // printf("Change directory to '%s'\n", cmdarr[1]); + if (chdir(cmdarr[1]) != 0) { + printf("\033[0;31mERROR - Could not change cwd\n\033[0m"); + } + continue; + } + + //work out if we need to exit + if (exitPrefix(cmdstr)) { + printf("Exited.\n"); + break; + } + + // try to find a binary + strcpy(cmdstr, cmdarr[0]); + bool binExists = false; + char cmdpath[512]; + for (i = 0; i < binlen + 1; i++) { + if (i >= binlen) { + strcpy(cmdpath, cwdbfr); + } else { + strcpy(cmdpath, bins[i]); + } + strcat(cmdpath, "/"); + strcat(cmdpath, cmdstr); + if (access(cmdpath, F_OK) != -1) { + binExists = true; + break; + } + } + if (!(binExists)) { + printf("Couldn't find binary - Looked in the following places:\n - %s\n", cwdbfr); + for (i = 0; i < binlen; i++) { + printf(" - %s\n", bins[i]); + } + continue; + } + // printf("Found binary at '%s'\n", cmdpath); + cmdarr[cmdlen] = NULL; + + pid_t pid = fork(); + bool success = true; + + if (pid == 0) { + // printf("Child Process: PID = %i, PPID = %i\n", getpid(), getppid()); + if (execvp(cmdpath, cmdarr) < 0) { + perror("\033[0;31mexec error "); + printf("\033[0m"); + success = false; + } + break; + + } else { + // printf("Parent Process: PID = %i, PPID = %i\n", getpid(), getppid()); + int status; + if (waitpid(pid, &status, 0) < 0) { + perror("\033[0;31mwaitpid error "); + printf("\033[0m"); + success = false; + } + if (success) { + printStatus(status); + } + } + } + return EXIT_SUCCESS; +} + +// prints out the status code of an exited process. +// prints in green if the status code is zero. anything +// else is red. +void printStatus(int status) { + if (status == 0) { + printf("\033[0;32m"); + } else { + printf("\033[0;31m"); + } + printf("[Process exited with status code %i]\n\033[0m", status); +} + +// returns an integer of how many times a char was found in a char +// array +int strcnt(char* str, const char cnt) { + int count = 0; + for (int i = 0; i < INT_MAX; i++) { + char c = str[i]; + if (c == '\0') { + break; + } + if (c == cnt) { + count++; + } + } + return count; +} + +// returns a boolean if a char array starts with the string "exit" +bool exitPrefix(const char* cmdstr) { + char fourChars[5]; + strncpy(fourChars, cmdstr, 4); + return strcmp(fourChars, "exit") == 0; +}
\ No newline at end of file @@ -0,0 +1,8 @@ +#ifndef SHELL_H +#define SHELL_H + +void printStatus(int status); +int strcnt(char* str, const char cnt); +bool exitPrefix(const char* cmdstr); + +#endif
\ No newline at end of file |