Write a shell with history capabilities

process_chp3/osh_shell/.gitignore

@@ -0,0 +1,2 @@
+osh_history
+osh

process_chp3/osh_shell/Makefile

@@ -0,0 +1,18 @@
+CC=gcc
+CFLAGS=-o osh -Wall
+SRCS=history.c osh.c
+
+.DEFAULT_GOAL := build
+
+build:
+	$(CC) $(CFLAGS) -fsanitize=address -static-libasan $(SRCS)
+	
+release:
+	$(CC) $(CFLAGS) $(SRCS)
+
+debug:
+	$(CC) $(CFLAGS) -fsanitize=address -static-libasan -ggdb $(SRCS)
+	gdb -q osh
+
+clean:
+	rm -f osh

process_chp3/osh_shell/history.c

@@ -0,0 +1,109 @@
+#include "history.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define HISTORY_FILENAME "osh_history"
+#define W_MODE "w"
+#define R_MODE "r"
+#define A_MODE "a+"
+
+int allocate_history(void) {
+  FILE *file;
+  if (access(HISTORY_FILENAME, F_OK) == -1) {
+    if ((file = fopen(HISTORY_FILENAME, W_MODE)) == NULL) {
+      perror("Error");
+      return -1;
+    }
+    fclose(file);
+  }
+
+  if ((file = fopen(HISTORY_FILENAME, R_MODE)) == NULL) {
+    perror("Error");
+    return -1;
+  }
+
+  int count = -1;
+  char line[MAXLEN];
+  while (!feof(file)) {
+    fgets(line, sizeof(line), file);
+    count++;
+  }
+
+  fclose(file);
+  return count;
+}
+
+history_entry_t *get_history(int history_count) {
+  FILE *file = fopen(HISTORY_FILENAME, R_MODE);
+  if (!file) {
+    perror("Error");
+    exit(EXIT_FAILURE);
+  }
+
+  int num = 0;
+  char line[MAXLEN];
+  const int offset = history_count - HISTORY_SIZE;
+  history_entry_t *history = calloc(HISTORY_SIZE, sizeof(history_entry_t));
+  while (fgets(line, sizeof(line), file)) {
+    if (num >= offset) {
+      history_entry_t entry;
+      entry.line_number = num + 1;
+      strcpy(entry.command, line);
+      history[num - offset] = entry;
+    }
+    num++;
+  }
+  fclose(file);
+  return history;
+}
+
+int add_history(int count, char *cmd) {
+  FILE *file = fopen(HISTORY_FILENAME, A_MODE);
+  if (!file) {
+    perror("Error");
+    exit(EXIT_FAILURE);
+  }
+
+  fprintf(file, "%s\n", cmd);
+  fclose(file);
+  return count + 1;
+}
+
+int last_command(char *last) {
+  FILE *file = fopen(HISTORY_FILENAME, A_MODE);
+  if (!file) {
+    perror("Error");
+    exit(EXIT_FAILURE);
+  }
+
+  char line[MAXLEN];
+  while (!feof(file)) {
+    fgets(line, sizeof(line), file);
+  }
+
+  fclose(file);
+  strcpy(last, line);
+  return 0;
+}
+
+int nth_command(char *s, int n) {
+  FILE *file = fopen(HISTORY_FILENAME, R_MODE);
+  if (!file) {
+    perror("Error");
+    exit(EXIT_FAILURE);
+  }
+
+  int num = 0;
+  char line[MAXLEN];
+  while (fgets(line, sizeof(line), file)) {
+    if ((num + 1) == n) {
+      strcpy(s, line);
+      return 0;
+    }
+    num++;
+  }
+  fclose(file);
+  return -1;
+}

process_chp3/osh_shell/history.h

@@ -0,0 +1,29 @@
+#ifndef __HISTORY_H__
+#define __HISTORY_H__
+
+#define MAXLEN 80
+#define HISTORY_SIZE 10
+
+typedef struct __HISTORY_ENTRY__ {
+  int line_number;
+  char command[MAXLEN];
+} history_entry_t;
+
+// Create new history file if not exists,
+// otherwise read last command count and return it
+int allocate_history(void);
+
+// Return last ten command in the history file
+history_entry_t *get_history(int);
+
+// Write a record in the history file
+int add_history(int, char *);
+
+// Read last command in the history file
+int last_command(char *);
+
+// Search nth command in the history file,
+// if not found nth command return -1.
+int nth_command(char *, int);
+
+#endif // __HISTORY_H__

process_chp3/osh_shell/osh.c

@@ -0,0 +1,147 @@
+#include "history.h"
+#include <ctype.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+struct command_t {
+  char **args;
+  bool bg_flag;
+};
+
+struct command_t parse_command(char *);
+int digits(char *);
+
+int main(void) {
+
+  // Create and/or read history file
+  int history_count = allocate_history();
+  if (history_count < 0) {
+    perror("Error");
+    exit(EXIT_FAILURE);
+  }
+
+  int should_run = 1;
+  while (should_run) {
+    char raw[MAXLEN / 2 + 1];
+    printf("osh> ");
+    fflush(stdout);
+    fgets(raw, MAXLEN / 2 + 1, stdin);
+
+    // check if user press newline
+    if (strcmp(raw, "\n") == 0) {
+      continue;
+    }
+
+    // FIXME: handle ^D shortcut
+    if (strcmp(raw, "\000") == 0) {
+      exit(EXIT_SUCCESS);
+    }
+
+    char *c;
+    if (strcmp(raw, "!!\n") == 0) {
+      if (nth_command(raw, history_count) != -1) {
+        printf("%s\n", raw);
+      } else {
+        printf("History is empty\n");
+        continue;
+      }
+    } else if ((c = strchr(raw, '!')) != NULL) {
+      const int n = digits(c);
+      if (nth_command(raw, n) != -1) {
+        printf("%s\n", raw);
+      } else {
+        printf("Command not found in position %d\n", n);
+        continue;
+      }
+    }
+
+    // remove carriage return
+    raw[strlen(raw) - 1] = '\0';
+
+    // save command in the history file
+    history_count = add_history(history_count, raw);
+
+    struct command_t cmd = parse_command(raw);
+    if (strcmp(cmd.args[0], "exit") == 0) {
+      should_run = 0;
+    } else if (strcmp(cmd.args[0], "history") == 0) {
+      // print on the stdout last 10 commands in reverse way
+      history_entry_t *history = get_history(history_count);
+      for (int i = HISTORY_SIZE - 1; i >= 0; i--) {
+        history_entry_t entry = history[i];
+        if (entry.line_number != 0) {
+          printf("%5d\t%s", entry.line_number, entry.command);
+        }
+      }
+
+      free(history);
+      history = NULL;
+    } else {
+      pid_t pid = fork();
+      switch (pid) {
+      case -1:
+        perror("Fork\n");
+        exit(EXIT_FAILURE);
+      case 0:
+        should_run = 0;
+        if (execvp(cmd.args[0], cmd.args)) {
+          perror("Error");
+        }
+        break;
+      default:
+        if (!cmd.bg_flag) {
+          wait(NULL);
+        }
+
+        break;
+      }
+    }
+
+    free(cmd.args);
+    cmd.args = NULL;
+  }
+
+  return EXIT_SUCCESS;
+}
+
+struct command_t parse_command(char *raw) {
+  int i = 0;
+  bool bg_flag = false;
+  char **args = (char **)calloc(MAXLEN, sizeof(char *));
+  char *tok = strtok(raw, " ");
+  while (tok != NULL) {
+    if (strcmp(tok, "&") == 0) {
+      bg_flag = true;
+    } else {
+      args[i] = tok;
+    }
+    tok = strtok(NULL, " ");
+    i++;
+  }
+
+  struct command_t cmd = {.args = args, .bg_flag = bg_flag};
+  return cmd;
+}
+
+int digits(char *s) {
+  char *sub = malloc(strlen(s) * sizeof(s));
+  char c;
+  int i = 0, j = 0;
+  while ((c = s[i]) != '\n') {
+    if (isdigit(c)) {
+      sub[j++] = c;
+    }
+    i++;
+  }
+
+  int n = atoi(sub);
+
+  free(sub);
+  sub = NULL;
+
+  return n;
+}