Add unix shell sample

README.md

@@ -38,5 +38,8 @@ Directory structure:
     - tasm/scripts - some common scripts for building and running examples with 
 DosBox
     - tasm/dos_input_hex - Example of input HEX byte in DL.
+* [**unix/shell**](https://github.com/edomin/samples/tree/master/unix/shell) - 
+envoking unix utils by typing its name in stdin. It is not complete shell 
+because it can not do piping and can not process shell syntax.
 
 Source code of samples released to public domain (license CC0).

unix/shell/.gitignore

@@ -0,0 +1 @@
+shell

unix/shell/Makefile

@@ -0,0 +1,14 @@
+CC = gcc
+CFLAGS = -Wall -Wextra -Wshadow -Wno-unused-parameter -Wno-unused-variable \
+ -O0 -ggdb
+LD = gcc
+LDFLAGS =
+
+shell: main.o
+	$(LD) $(LDFLAGS) -o shell main.o
+
+main.o: main.c
+	$(CC) $(CFLAGS) -c main.c -o main.o
+
+run: shell
+	./shell

unix/shell/main.c

@@ -0,0 +1,178 @@
+#include <ctype.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#define COMMAND_LEN_MAX 1024
+#define TOKEN_LEN_MAX COMMAND_LEN_MAX
+#define TOKENS_MAX      256
+
+/* https://gist.github.com/Fonger/98cc95ac39fbe1a7e4d9 */
+size_t strlcat(char *dst, const char *src, size_t size) {
+    size_t srclen;
+    size_t dstlen;
+
+    dstlen = strlen(dst);
+    size -= dstlen + 1;
+
+    if (!size)
+        return (dstlen);
+
+    srclen = strlen(src);
+
+    if (srclen > size)
+        srclen = size;
+
+    memcpy(dst + dstlen, src, srclen);
+    dst[dstlen + srclen] = '\0';
+
+    return (dstlen + srclen);
+}
+
+size_t strlcpy(char *dst, const char *src, size_t size) {
+    size_t srclen;
+
+    size --;
+
+    srclen = strlen(src);
+
+    if (srclen > size)
+        srclen = size;
+
+    memcpy(dst, src, srclen);
+    dst[srclen] = '\0';
+
+    return (srclen);
+}
+
+void Prompt(void) {
+    char username[LOGIN_NAME_MAX];
+    char hostname[HOST_NAME_MAX];
+    char workingDir[PATH_MAX];
+    size_t promptMax = LOGIN_NAME_MAX + HOST_NAME_MAX + PATH_MAX + 4;
+    char prompt[promptMax];
+
+    getlogin_r(username, LOGIN_NAME_MAX);
+    gethostname(hostname, HOST_NAME_MAX);
+    getcwd(workingDir, PATH_MAX);
+
+    strlcpy(prompt, username, promptMax);
+    strlcat(prompt, "@", promptMax);
+    strlcat(prompt, hostname, promptMax);
+    strlcat(prompt, ":", promptMax);
+    strlcat(prompt, workingDir, promptMax);
+    strlcat(prompt, "$ ", promptMax);
+
+    printf("%s", prompt);
+}
+
+void ReadCommand(char *command, size_t len) {
+    fgets(command, len, stdin);
+    command[strlen(command) - 1] = '\0';
+}
+
+void Tokenize(char *command, char **tokens, size_t *tokensCount,
+ size_t tokensMax, size_t tokenLenMax) {
+    char *pch;
+
+    *tokensCount = 0;
+
+    pch = strtok(command," ");
+    while (pch != NULL) {
+        strlcpy(tokens[*tokensCount], pch, tokenLenMax);
+        pch = strtok(NULL, " ");
+        (*tokensCount)++;
+        if (*tokensCount > tokensMax)
+            break;
+    }
+}
+
+bool IsNumber(char *str, size_t len) {
+    bool number = true;
+
+    for (size_t i = 0; i < len; i++) {
+        if (str[i] == '\0') {
+            if (i == 0) {
+                number = false;
+            }
+            break;
+        }
+        if (!isdigit(str[i])) {
+            number = false;
+            break;
+        }
+    }
+
+    return number;
+}
+
+void InitTokens(char **tokens, size_t len) {
+    for (size_t i = 0; i < len; i++) {
+        tokens[i] = NULL;
+    }
+}
+
+void RefreshTokens(char **tokens, size_t len) {
+    for (size_t i = 0; i < len; i++) {
+        if (tokens[i] == NULL)
+            tokens[i] = malloc(sizeof(char) * len);
+    }
+}
+
+void NullTerminateTokens(char **tokens, size_t len, size_t tokensCount) {
+    for (size_t i = tokensCount; i < len; i++) {
+        free(tokens[i]);
+        tokens[i] = NULL;
+    }
+}
+
+int main(int argc, char **argv) {
+    char   command[COMMAND_LEN_MAX];
+    char **tokens = malloc(sizeof(char *) * TOKENS_MAX);
+    size_t tokensCount;
+    int    status;
+    int    exitStatus = 0;
+
+    InitTokens(tokens, TOKENS_MAX);
+
+    while (true) {
+        RefreshTokens(tokens, TOKENS_MAX);
+
+        Prompt();
+        ReadCommand(command, COMMAND_LEN_MAX);
+        Tokenize(command, tokens, &tokensCount, TOKENS_MAX, TOKEN_LEN_MAX);
+
+        NullTerminateTokens(tokens, TOKENS_MAX, tokensCount);
+
+        if (strncmp(tokens[0], "exit", TOKEN_LEN_MAX) == 0) {
+            if (tokens[1] == NULL) {
+                return exitStatus;
+            } else {
+                if (IsNumber(tokens[1], TOKEN_LEN_MAX))
+                    return strtol(tokens[1], NULL, 10);
+                else
+                    return exitStatus;
+            }
+        }
+
+        if (fork() != 0) {
+            /* parent */
+            waitpid(-1, &status, 0);
+            exitStatus = WEXITSTATUS(status);
+        } else {
+            /* child */
+            int ret = execvp(tokens[0], tokens);
+            if (ret != 0) {
+                perror("execve");
+                return 0;
+            }
+        }
+    }
+
+    return 0;
+}