README.md

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+# arsh
+
+Simple shell for Unix-like systems written in C

README.org

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-#+title: arsh - ARchaic SHell
-#+options: toc:nil
-Simple shell for Unix-like systems written in C, that has a funny name (for germans).
-* Features
-- Can run one command at a given time (no | , &&, ||, functions, etc)
-- ~cd~ builtin command
-- ~exit~ builtin command
-* Build
-To build it, you need ~readline~ library. Then use
-#+begin_src shell
-gcc main.c -O3 -lreadline -o arsh
-#+end_src 

main.c

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-#include <stdlib.h>
-#include <string.h>
-#include <unistd.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <readline/readline.h>
-#include <sys/wait.h>
-#include <signal.h>
-#include <setjmp.h>
-
-static sigjmp_buf restart_jmp_buf;
-static const int restart_value = 69;
-static volatile sig_atomic_t jump_active = 0;
-
-void sigint_handler(int signo)
-{
-  if(!jump_active)
-  {
-    return;
-  }
-  siglongjmp(restart_jmp_buf, restart_value);
-}
-
-char** split_input(char* input)
-{
-  const size_t alloc_size = ((strlen(input) + 1) / 2) + 1;
-  char** command = malloc(alloc_size * sizeof(char*));
-  if (command == NULL)
-  {
-    perror("malloc failed");
-    exit(1);
-  }
-  const char* separator = " ";
-  char* parsed;
-  uint32_t index = 0;
-  parsed = strtok(input, separator);
-  while (parsed != NULL)
-  {
-    command[index] = parsed;
-    index++;
-    parsed = strtok(NULL, separator);
-  }
-  command[index] = NULL;
-  return command;
-}
-
-int cd(char* path)
-{
-  return chdir(path);
-}
-
-int main()
-{
-  struct sigaction s;
-  s.sa_handler = sigint_handler;
-  sigemptyset(&s.sa_mask);
-  s.sa_flags = SA_RESTART;
-  struct sigaction s_old;
-  sigaction(SIGINT, &s, &s_old);
-
-  int stat_loc;
-
-  if(sigsetjmp(restart_jmp_buf, 1) == restart_value)
-  {
-    printf("\n");
-  }
-  jump_active = 1;
-  
-  while(true)
-  {
-    char* input = readline("arsh> ");
-    if(input == NULL) //CTRL + D
-    {
-      continue;
-    }
-    char** command = split_input(input);
-    
-    if(strcmp(command[0], "cd") == 0)
-    {
-      if (cd(command[1]) < 0)
-      {
-	perror(command[1]);
-      }
-
-      continue; //skip fork()
-    }
-    if(strcmp(command[0], "exit") == 0)
-    {
-      int32_t status_code = command[1] != NULL ? atoi(command[1]) : 0;
-      exit(status_code);
-    }
-    
-    pid_t child_pid = fork();
-    if (child_pid < 0) 
-    {
-      perror("Fork failed");
-      exit(1);
-    }
-    if (child_pid == 0)
-    {
-      sigaction(SIGINT, &s_old, NULL);
-      //never returns if call is successful
-      if(execvp(command[0], command) < 0)
-      {
-	perror(command[0]);
-	exit(1);
-      }
-    }
-    else
-    {
-      waitpid(child_pid, &stat_loc, WUNTRACED);
-    }
-
-    free(input);
-    free(command);
-  }
-}