initial

.gitignore

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+bin/

Makefile

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+TARGET=s
+BUILDDIR=bin/
+PREFIX=/usr/local/bin/
+SOURCES=$(wildcard src/*.c)
+MAIN=main.c
+override LDFLAGS+=-ledit
+override CFLAGS+=-Werror -Wall -g -fPIC -O2 -DNDEBUG -ftrapv -Wfloat-equal -Wundef -Wwrite-strings -Wuninitialized -pedantic -std=c11
+
+all: main.c
+	mkdir -p $(BUILDDIR)
+	$(CC) $(MAIN) $(SOURCES) -o $(BUILDDIR)$(TARGET) $(CFLAGS) $(LDFLAGS)
+
+install: all
+	install $(BUILDDIR)$(TARGET) $(PREFIX)$(TARGET)
+
+uninstall:
+	rm -rf $(PREFIX)$(TARGET)

README.md

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+# s
+
+A minimal shell.

main.c

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+#include "src/shell.h"
+
+int main(int argc, char** argv) {
+  s_loop();
+
+  return 0;
+}

src/builtins.c

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+#include "builtins.h"
+
+const char* s_builtin_names[] = {"cd", "exit"};
+s_builtin s_builtins[] = {&s_cd, &s_exit};
+
+int s_cd(char** args) {
+  if (!args[1]) {
+    s_error("cd", "expected argument");
+  } else {
+    if (chdir(args[1])) perror("s");
+  }
+  return 1;
+}
+
+int s_exit(char** args) {
+  return 0;
+}
+
+int s_builtins_count() {
+  return sizeof(s_builtin_names) / sizeof(const char *);
+}

src/builtins.h

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+#include <unistd.h>
+
+#include "util.h"
+
+typedef int (*s_builtin)(char**);
+
+int s_cd(char**);
+int s_exit(char**);
+int s_builtins_count();
+
+extern const char* s_builtin_names[];
+extern s_builtin s_builtins[];

src/shell.c

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+#include "shell.h"
+
+void s_die(const char* msg) {
+  fprintf(stderr, "s: %s\n", msg);
+  exit(1);
+}
+
+int s_do(char **args) {
+  pid_t pid, wpid;
+  int s;
+
+  pid = fork();
+  if (!pid) {
+    if (execvp(args[0], args) == -1) perror("lsh");
+    exit(EXIT_FAILURE);
+  } else if (pid < 0) {
+    // Error forking
+    perror("lsh");
+  } else {
+    do {
+      wpid = waitpid(pid, &s, WUNTRACED);
+    } while (!WIFEXITED(s) && !WIFSIGNALED(s));
+  }
+
+  return 1;
+}
+
+
+char** s_prompt() {
+  char* line = readline("> ");
+  int bs = 64;
+  int pos = 0;
+  char **tokens = malloc(bs * sizeof(char*));
+  char *token;
+
+
+  if (!line) return NULL;
+
+  add_history(line);
+
+  if (!tokens) s_die("allocation error");
+
+  token = strtok(line, " \t\r\n\a");
+
+  while (token) {
+    tokens[pos++] = token;
+
+    if (pos >= bs) {
+      bs += 64;
+      tokens = realloc(tokens, bs * sizeof(char*));
+      if (!tokens) s_die("allocation error");
+    }
+
+    token = strtok(NULL, " \t\r\n\a");
+  }
+  tokens[pos] = NULL;
+
+  free(line);
+  return tokens;
+}
+
+int s_exec(char** args) {
+  int i;
+
+  if (!args[0]) return 1;
+
+  for (i = 0; i < s_builtins_count(); i++) {
+    if (!strcmp(args[0], s_builtin_names[i])) return (*s_builtins[i])(args);
+  }
+
+  return s_do(args);
+}
+
+void s_loop() {
+  char** cmd;
+  int s;
+
+  do {
+    cmd = s_prompt();
+    if(!cmd) return;
+    s = s_exec(cmd);
+    free(cmd);
+  } while(s);
+}

src/shell.h

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+#include <stdlib.h>
+#include <string.h>
+
+#include <editline/readline.h>
+
+#include "builtins.h"
+
+void s_loop();
+char** s_prompt();
+int s_exec(char**);

src/util.c

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+#include "util.h"
+
+void s_error(const char* cmd, const char* msg) {
+  fprintf(stderr, "%s: %s\n", cmd, msg);
+}

src/util.h

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+#include <stdio.h>
+
+void s_error(const char*, const char*);