152 lines
3.0 KiB
C
152 lines
3.0 KiB
C
#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 <time.h>
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#include <sys/types.h>
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#define PROMPT "msh> "
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#define EXIT_CMD "exit"
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#define MAX_BUF 121
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// Statuses from builtin responses
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#define RESP_HELP 1
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#define RESP_DATE 2
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#define RESP_ECHO 3
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#define RESP_SHELL 4
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#define RESP_CD_FAIL -1
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#define RESP_CD_SUCCESS 6
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// Sub statuses that are generally nice to have
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#define CD_NOP 0x1
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void echo(const char*);
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void remove_newline(char*);
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void exit_branch(const char*);
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int builtin_response(char*);
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int cd_handler(char**, const int);
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int main(int argc, char** argv) {
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FILE* file = NULL;
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if(argc == 2) {
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file = fopen(argv[1], "r");
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if(!file) { return 1; }
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}
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char buffer[MAX_BUF];
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while(1) {
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// determine if we're reading from stdin or a stream of some sort
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if(file == NULL && isatty(STDIN_FILENO)) {
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printf("%s", PROMPT);
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fgets(buffer, MAX_BUF, stdin);
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}
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else {
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fgets(buffer, MAX_BUF, file);
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printf("buffer: %s\n", buffer);
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}
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// Deal with EOF input
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if(!strlen(buffer)) {
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exit(0);
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}
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exit_branch(buffer);
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remove_newline(buffer);
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int status = builtin_response(buffer);
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// the switch in case we need to add more response flags later
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switch(status) {
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case RESP_ECHO:
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echo(buffer);
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case RESP_SHELL: // shell command handler was used
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continue;
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case RESP_CD_FAIL:
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printf("msh: cd: No such file or directory\n");
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}
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memset(buffer, 0x00, MAX_BUF); // reset buffer after each usage
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}
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return 0;
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}
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void echo(const char* buf) {
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printf("%s\n", buf);
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}
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void remove_newline(char* buf) {
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char* c = buf;
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while(*c != '\n') { c++; }
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*c='\0';
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}
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void exit_branch(const char* buf) {
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if(!strcmp(buf, EXIT_CMD)) {
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exit(0);
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}
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}
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int builtin_response(char* buffer) {
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#define STRING_DELIMITER " "
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#define TIME_FMT "%D"
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exit_branch(buffer); // exit is builtin so here we are
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if(!strcmp(buffer, "help")) {
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echo("enter Linux commands, or ‘exit’ to exit");
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return RESP_HELP;
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}
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// Printout the date today
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if(!strcmp(buffer, "date")) {
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static char date[64];
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time_t now = time(0);
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strftime(date, sizeof(date), TIME_FMT, localtime(&now));
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echo(date);
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return RESP_DATE;
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}
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// Populate tokens
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char *tokens[64];
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int idx = 0;
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for(char* cur = strtok(buffer, STRING_DELIMITER); cur != NULL; cur=strtok(NULL, STRING_DELIMITER)) {
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#ifdef DBG_LINE
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printf("%s ", cur);
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#endif
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tokens[idx] = cur;
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idx++;
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}
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// Handling director changes
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int cd_result = cd_handler(tokens, idx);
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if(cd_result != CD_NOP) {
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return cd_result;
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}
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// Execute child process
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pid_t child = fork();
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if(child != 0) {
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int status_child = wait(NULL);
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if(status_child == 127) {
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printf("msh: %s: %d", tokens[0], status_child);
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}
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}
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else {
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execvp(tokens[0], tokens);
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}
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// Cleanup pointers
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for(int i = 0; i< 64; i++) {
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tokens[i] = NULL;
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}
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}
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int cd_handler(char** tokens, const int t_count) {
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if(!strcmp(tokens[0], "cd")) {
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if(t_count < 2) {
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int ret = chdir(getenv("HOME"));
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return ret;
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}
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return chdir(tokens[1]);
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}
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return CD_NOP;
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}
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