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c75b586829
toaruos/apps/sh.c
K. Lange c75b586829 Fix some error handling
2018-07-18 09:43:39 +09:00

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22 KiB
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/* vim: tabstop=4 shiftwidth=4 noexpandtab
* This file is part of ToaruOS and is released under the terms
* of the NCSA / University of Illinois License - see LICENSE.md
* Copyright (C) 2013-2018 K. Lange
*
* E-Shell
*
* This is the "experimental shell". It provides
* a somewhat unix-like shell environment, but does
* not include a parser any advanced functionality.
* It simply cuts its input into arguments and executes
* programs.
*/
#define _XOPEN_SOURCE
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <dirent.h>
#include <signal.h>
#include <getopt.h>
#include <termios.h>
#include <errno.h>
#include <fcntl.h>
#include <ctype.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/utsname.h>
#include <sys/stat.h>
#include <_xlog.h>
#include <toaru/list.h>
#include <toaru/kbd.h>
#include <toaru/rline.h>
#define PIPE_TOKEN "\xFF\xFFPIPE\xFF\xFF"
#define STAR_TOKEN "\xFF\xFFSTAR\xFF\xFF"
#define WRITE_TOKEN "\xFF\xFFWRITE\xFF\xFF"
#define APPEND_TOKEN "\xFF\xFF""APPEND\xFF"
/* A shell command is like a C program */
typedef uint32_t(*shell_command_t) (int argc, char ** argv);
/* We have a static array that fits a certain number of them. */
#define SHELL_COMMANDS 512
char * shell_commands[SHELL_COMMANDS]; /* Command names */
shell_command_t shell_pointers[SHELL_COMMANDS]; /* Command functions */
char * shell_descript[SHELL_COMMANDS]; /* Command descriptions */
/* This is the number of actual commands installed */
int shell_commands_len = 0;
int shell_interactive = 1;
int last_ret = 0;
char ** shell_argv = NULL;
int shell_argc = 0;
int pid; /* Process ID of the shell */
void shell_install_command(char * name, shell_command_t func, char * desc) {
if (shell_commands_len == SHELL_COMMANDS) {
fprintf(stderr, "Ran out of space for static shell commands. The maximum number of commands is %d\n", SHELL_COMMANDS);
return;
}
shell_commands[shell_commands_len] = name;
shell_pointers[shell_commands_len] = func;
shell_descript[shell_commands_len] = desc;
shell_commands_len++;
}
shell_command_t shell_find(char * str) {
for (int i = 0; i < shell_commands_len; ++i) {
if (!strcmp(str, shell_commands[i])) {
return shell_pointers[i];
}
}
return NULL;
}
void install_commands();
/* Maximum command length */
#define LINE_LEN 4096
/* Current working directory */
char cwd[1024] = {'/',0};
/* Username */
char username[1024];
/* Hostname for prompt */
char _hostname[256];
/* function to update the cached username */
void getuser() {
char * tmp = getenv("USER");
if (tmp) {
_XLOG("Got user:");
_XLOG(tmp);
strcpy(username, tmp);
} else {
sprintf(username, "%d", getuid());
}
}
/* function to update the cached hostname */
void gethost() {
struct utsname buf;
uname(&buf);
int len = strlen(buf.nodename);
memcpy(_hostname, buf.nodename, len+1);
}
/* Draw the user prompt */
void draw_prompt(int ret) {
/* Get the time */
struct tm * timeinfo;
struct timeval now;
gettimeofday(&now, NULL); //time(NULL);
timeinfo = localtime((time_t *)&now.tv_sec);
/* Format the date and time for prompt display */
char date_buffer[80];
strftime(date_buffer, 80, "%m/%d", timeinfo);
char time_buffer[80];
strftime(time_buffer, 80, "%H:%M:%S", timeinfo);
/* Print the working directory in there, too */
getcwd(cwd, 512);
char _cwd[512];
strcpy(_cwd, cwd);
char * home = getenv("HOME");
if (home && strstr(cwd, home) == cwd) {
char * c = cwd + strlen(home);
if (*c == '/' || *c == 0) {
sprintf(_cwd, "~%s", c);
}
}
/* Print the prompt. */
printf("\033]1;%s@%s:%s\007", username, _hostname, _cwd);
printf("\033[1m\033[s\033[400C\033[16D\033[1m\033[38;5;59m[\033[38;5;173m%s \033[38;5;167m%s\033[38;5;59m]\033[u\033[38;5;221m%s\033[38;5;59m@\033[38;5;81m%s ",
date_buffer, time_buffer,
username, _hostname);
if (ret != 0) {
printf("\033[38;5;167m%d ", ret);
}
printf("\033[0m%s%s\033[0m ", _cwd, getuid() == 0 ? "\033[1;38;5;196m#" : "\033[1;38;5;47m$");
fflush(stdout);
}
uint32_t child = 0;
void sig_pass(int sig) {
/* Interrupt handler */
if (child) {
kill(child, sig);
}
}
void redraw_prompt_func(rline_context_t * context) {
draw_prompt(last_ret);
}
void draw_prompt_c() {
printf("> ");
fflush(stdout);
}
void redraw_prompt_func_c(rline_context_t * context) {
draw_prompt_c();
}
void tab_complete_func(rline_context_t * c) {
char * dup = malloc(LINE_LEN);
memcpy(dup, c->buffer, LINE_LEN);
char *pch, *save;
char *argv[1024];
int argc = 0;
int cursor = 0;
pch = strtok_r(dup, " ", &save);
if (!pch) {
argv[0] = "";
argc = 0;
}
while (pch != NULL) {
if (pch - dup <= c->offset) cursor = argc;
argv[argc] = pch;
++argc;
pch = strtok_r(NULL, " ", &save);
}
argv[argc] = NULL;
if (c->offset && c->buffer[c->offset-1] == ' ' && argc) {
cursor++;
}
char * word = argv[cursor];
int word_offset = word ? (c->offset - (argv[cursor] - dup)) : 0;
char * prefix = malloc(word_offset + 1);
if (word) memcpy(prefix, word, word_offset);
prefix[word_offset] = '\0';
/* Complete file path */
list_t * matches = list_create();
char * match = NULL;
int free_matches = 0;
int no_space_if_only = 0;
if (cursor == 0 && !strchr(prefix,'/')) {
/* Complete binary name */
for (int i = 0; i < shell_commands_len; ++i) {
if (strstr(shell_commands[i], prefix) == shell_commands[i]) {
list_insert(matches, shell_commands[i]);
match = shell_commands[i];
}
}
} else {
free_matches = 1;
char * tmp = strdup(prefix);
char * last_slash = strrchr(tmp, '/');
DIR * dirp;
char * compare = prefix;
if (last_slash) {
*last_slash = '\0';
word = word + (last_slash - tmp) + 1;
word_offset = word_offset - (last_slash - tmp + 1);
compare = word;
if (last_slash == tmp) {
dirp = opendir("/");
} else {
dirp = opendir(tmp);
}
} else {
dirp = opendir(".");
}
if (!dirp) {
free(tmp);
goto finish_tab;
}
struct dirent * ent = readdir(dirp);
while (ent != NULL) {
if (ent->d_name[0] != '.') {
if (!word || strstr(ent->d_name, compare) == ent->d_name) {
struct stat statbuf;
/* stat it */
if (last_slash) {
char * x = malloc(strlen(tmp) + 1 + strlen(ent->d_name) + 1);
sprintf(x,"%s/%s",tmp,ent->d_name);
lstat(x, &statbuf);
} else {
lstat(ent->d_name, &statbuf);
}
char * s;
if (S_ISDIR(statbuf.st_mode)) {
s = malloc(strlen(ent->d_name) + 2);
sprintf(s,"%s/", ent->d_name);
no_space_if_only = 1;
} else {
s = strdup(ent->d_name);
}
list_insert(matches, s);
match = s;
}
}
ent = readdir(dirp);
}
closedir(dirp);
free(tmp);
}
if (matches->length == 1) {
/* Insert */
rline_insert(c, &match[word_offset]);
if (word && word_offset == (int)strlen(word) && !no_space_if_only) {
rline_insert(c, " ");
}
rline_redraw(c);
} else if (matches->length > 1) {
if (!c->tabbed) {
/* see if there is a minimum subset we can fill in */
size_t j = word_offset;
do {
char d = match[j];
int diff = 0;
foreach(node, matches) {
char * match = (char *)node->value;
if (match[j] != d || match[j] == '\0') diff = 1;
}
if (diff) break;
j++;
} while (j < (size_t)c->requested);
if (j > (size_t)word_offset) {
char * tmp = strdup(match);
tmp[j] = '\0';
rline_insert(c, &tmp[word_offset]);
rline_redraw(c);
free(tmp);
} else {
c->tabbed = 1;
}
} else {
/* Print matches */
fprintf(stderr,"\n");
size_t j = 0;
foreach(node, matches) {
char * match = (char *)node->value;
fprintf(stderr, "%s", match);
++j;
if (j < matches->length) {
fprintf(stderr, ", ");
}
}
fprintf(stderr,"\n");
c->callbacks->redraw_prompt(c);
fprintf(stderr, "\033[s");
rline_redraw(c);
}
}
finish_tab:
if (free_matches) list_destroy(matches);
list_free(matches);
free(prefix);
free(dup);
}
void add_argument(list_t * argv, char * buf) {
char * c = malloc(strlen(buf) + 1);
memcpy(c, buf, strlen(buf) + 1);
list_insert(argv, c);
}
int read_entry(char * buffer) {
rline_callbacks_t callbacks = {
tab_complete_func, redraw_prompt_func, NULL,
NULL, NULL, NULL, NULL, NULL
};
int buffer_size = rline((char *)buffer, LINE_LEN, &callbacks);
return buffer_size;
}
int read_entry_continued(char * buffer) {
rline_callbacks_t callbacks = {
tab_complete_func, redraw_prompt_func_c, NULL,
NULL, NULL, NULL, NULL, NULL
};
int buffer_size = rline((char *)buffer, LINE_LEN, &callbacks);
return buffer_size;
}
int variable_char(uint8_t c) {
if (c >= 'A' && c <= 'Z') return 1;
if (c >= 'a' && c <= 'z') return 1;
if (c >= '0' && c <= '9') return 1;
if (c == '_') return 1;
if (c == '?') return 1;
return 0;
}
void run_cmd(char ** args) {
int i = execvp(*args, args);
shell_command_t func = shell_find(*args);
if (func) {
int argc = 0;
while (args[argc]) {
argc++;
}
i = func(argc, args);
} else {
if (i != 0) {
fprintf(stderr, "%s: Command not found\n", *args);
i = 127;
}
}
exit(i);
}
int is_number(const char * c) {
while (*c) {
if (!isdigit(*c)) return 0;
c++;
}
return 1;
}
int shell_exec(char * buffer, size_t size, FILE * file) {
/* Read previous history entries */
if (buffer[0] == '!') {
int x = atoi((char *)((uintptr_t)buffer + 1));
if (x > 0 && x <= rline_history_count) {
buffer = rline_history_get(x - 1);
} else {
fprintf(stderr, "esh: !%d: event not found\n", x);
return 0;
}
}
char * history = malloc(strlen(buffer) + 1);
memcpy(history, buffer, strlen(buffer) + 1);
if (buffer[0] != ' ' && buffer[0] != '\n') {
rline_history_insert(history);
} else {
free(history);
}
char * argv[1024];
int tokenid = 0;
char quoted = 0;
char backtick = 0;
char buffer_[512] = {0};
int collected = 0;
list_t * args = list_create();
int have_star = 0;
while (1) {
char * p = buffer;
while (*p) {
switch (*p) {
case '$':
if (quoted == '\'') {
goto _just_add;
} else {
if (backtick) {
goto _just_add;
}
p++;
char var[100];
int coll = 0;
if (*p == '{') {
p++;
while (*p != '}' && *p != '\0' && (coll < 100)) {
var[coll] = *p;
coll++;
var[coll] = '\0';
p++;
}
if (*p == '}') {
p++;
}
} else {
while (*p != '\0' && variable_char(*p) && (coll < 100)) {
var[coll] = *p;
coll++;
var[coll] = '\0';
if (coll == 0 && (isdigit(*p) || *p == '?')) {
p++;
break; /* Don't let these keep going */
}
p++;
}
}
/* Special cases */
char *c = NULL;
char tmp[128];
if (!strcmp(var, "?")) {
sprintf(tmp,"%d",last_ret);
c = tmp;
} else if (is_number(var)) {
int a = atoi(var);
if (a >= 0 && a < shell_argc) {
c = shell_argv[a];
}
} else {
c = getenv(var);
}
if (c) {
backtick = 0;
for (int i = 0; i < (int)strlen(c); ++i) {
buffer_[collected] = c[i];
collected++;
}
buffer_[collected] = '\0';
}
continue;
}
case '\"':
if (quoted == '\"') {
if (backtick) {
goto _just_add;
}
quoted = 0;
goto _next;
} else if (!quoted) {
quoted = *p;
goto _next;
}
goto _just_add;
case '\'':
if (quoted == '\'') {
if (backtick) {
goto _just_add;
}
quoted = 0;
goto _next;
} else if (!quoted) {
quoted = *p;
goto _next;
}
goto _just_add;
case '*':
if (quoted) {
goto _just_add;
}
if (backtick) {
goto _just_add;
}
if (have_star) {
goto _just_add; /* TODO multiple globs */
}
have_star = 1;
collected += sprintf(&buffer_[collected], STAR_TOKEN);
goto _next;
case '\\':
if (quoted == '\'') {
goto _just_add;
}
if (backtick) {
goto _just_add;
}
backtick = 1;
goto _next;
case ' ':
if (backtick) {
goto _just_add;
}
if (!quoted) {
goto _new_arg;
}
goto _just_add;
case '\n':
if (!quoted) {
goto _done;
}
goto _just_add;
case '|':
if (!quoted && !backtick) {
if (collected) {
add_argument(args, buffer_);
}
collected = sprintf(buffer_, "%s", PIPE_TOKEN);
goto _new_arg;
}
goto _just_add;
case '>':
if (!quoted && !backtick) {
if (collected) {
add_argument(args, buffer_);
}
collected = sprintf(buffer_, "%s", WRITE_TOKEN);
goto _new_arg;
}
goto _just_add;
case '#':
if (!quoted && !backtick && !collected) {
goto _done; /* Support comments; must not be part of an existing arg */
}
goto _just_add;
default:
if (backtick) {
buffer_[collected] = '\\';
collected++;
buffer_[collected] = '\0';
}
_just_add:
backtick = 0;
buffer_[collected] = *p;
collected++;
buffer_[collected] = '\0';
goto _next;
}
_new_arg:
backtick = 0;
if (collected) {
add_argument(args, buffer_);
buffer_[0] = '\0';
have_star = 0;
collected = 0;
}
_next:
p++;
}
_done:
if (quoted) {
if (shell_interactive == 1) {
draw_prompt_c();
read_entry_continued(buffer);
rline_history_append_line(buffer);
continue;
} else if (shell_interactive == 2) {
fgets(buffer, size, file);
continue;
} else {
fprintf(stderr, "Syntax error: Unterminated quoted string.\n");
return 127;
}
}
if (collected) {
add_argument(args, buffer_);
break;
}
break;
}
int cmdi = 0;
char ** arg_starts[100] = { &argv[0], NULL };
char * output_files[100] = { NULL };
int file_args[100] = {0};
int argcs[100] = {0};
int next_is_file = 0;
int i = 0;
foreach(node, args) {
char * c = node->value;
if (next_is_file) {
if (next_is_file == 1 && !strcmp(c, WRITE_TOKEN)) {
next_is_file = 2;
file_args[cmdi] = O_WRONLY | O_CREAT | O_APPEND;
continue;
}
output_files[cmdi] = c;
continue;
}
if (!strcmp(c, WRITE_TOKEN)) {
next_is_file = 1;
file_args[cmdi] = O_WRONLY | O_CREAT | O_TRUNC;
continue;
}
if (!strcmp(c, PIPE_TOKEN)) {
argv[i] = 0;
i++;
cmdi++;
arg_starts[cmdi] = &argv[i];
continue;
}
char * glob = strstr(c, STAR_TOKEN);
if (glob) {
/* Globbing */
glob[0] = '\0';
glob[1] = '\0';
char * before = c;
char * after = &glob[8];
int has_before = !!strlen(before);
int has_after = !!strlen(after);
if (!has_before || !strchr(before,'/')) {
/* read current directory, add all */
DIR * dirp = opendir(".");
int before_i = i;
struct dirent * ent = readdir(dirp);
while (ent != NULL) {
if (ent->d_name[0] != '.') {
char * s = malloc(sizeof(char) * (strlen(ent->d_name) + 1));
memcpy(s, ent->d_name, strlen(ent->d_name) + 1);
char * t = s;
if (has_before) {
if (strstr(s,before) != s) {
goto _nope;
}
t = &s[strlen(before)];
}
if (has_after) {
if (strlen(t) >= strlen(after)) {
if (!strcmp(after,&t[strlen(t)-strlen(after)])) {
argv[i] = s;
i++;
argcs[cmdi]++;
}
}
} else {
argv[i] = s;
i++;
argcs[cmdi]++;
}
}
_nope:
ent = readdir(dirp);
}
closedir(dirp);
if (before_i == i) {
/* no matches */
glob[0] = '*';
memmove(&glob[1], after, strlen(after)+1);
argv[i] = c;
i++;
argcs[cmdi]++;
} else {
free(c);
}
} else {
/* directory globs not supported */
glob[0] = '*';
argv[i] = c;
i++;
argcs[cmdi]++;
}
} else {
argv[i] = c;
i++;
argcs[cmdi]++;
}
}
argv[i] = NULL;
if (i == 0) {
return -1;
}
list_free(args);
char * cmd = *arg_starts[0];
tokenid = i;
unsigned int child_pid;
int nowait = (!strcmp(argv[tokenid-1],"&"));
if (nowait) {
argv[tokenid-1] = NULL;
}
if (cmdi > 0) {
int last_output[2];
pipe(last_output);
child_pid = fork();
if (!child_pid) {
dup2(last_output[1], STDOUT_FILENO);
close(last_output[0]);
run_cmd(arg_starts[0]);
}
for (int j = 1; j < cmdi; ++j) {
int tmp_out[2];
pipe(tmp_out);
if (!fork()) {
dup2(tmp_out[1], STDOUT_FILENO);
dup2(last_output[0], STDIN_FILENO);
close(tmp_out[0]);
close(last_output[1]);
run_cmd(arg_starts[j]);
}
close(last_output[0]);
close(last_output[1]);
last_output[0] = tmp_out[0];
last_output[1] = tmp_out[1];
}
if (!fork()) {
if (output_files[cmdi]) {
dup2(open(output_files[cmdi], file_args[cmdi], 0666), STDOUT_FILENO);
}
dup2(last_output[0], STDIN_FILENO);
close(last_output[1]);
run_cmd(arg_starts[cmdi]);
}
close(last_output[0]);
close(last_output[1]);
/* Now execute the last piece and wait on all of them */
} else {
shell_command_t func = shell_find(*arg_starts[0]);
if (func) {
return func(argcs[0], arg_starts[0]);
} else {
child_pid = fork();
if (!child_pid) {
if (output_files[cmdi]) {
dup2(open(output_files[cmdi], file_args[cmdi], 0666), STDOUT_FILENO);
}
run_cmd(arg_starts[0]);
}
}
}
tcsetpgrp(STDIN_FILENO, child_pid);
int ret_code = 0;
if (!nowait) {
child = child_pid;
int pid;
do {
pid = waitpid(-1, &ret_code, 0);
} while (pid != -1 || (pid == -1 && errno != ECHILD));
child = 0;
}
tcsetpgrp(STDIN_FILENO, getpid());
free(cmd);
return ret_code;
}
void add_path_contents(char * path) {
DIR * dirp = opendir(path);
if (!dirp) return; /* Failed to load directly */
struct dirent * ent = readdir(dirp);
while (ent != NULL) {
if (ent->d_name[0] != '.') {
char * s = malloc(sizeof(char) * (strlen(ent->d_name) + 1));
memcpy(s, ent->d_name, strlen(ent->d_name) + 1);
shell_install_command(s, NULL, NULL);
}
ent = readdir(dirp);
}
closedir(dirp);
}
struct command {
char * string;
void * func;
char * desc;
};
static int comp_shell_commands(const void *p1, const void *p2) {
return strcmp(((struct command *)p1)->string, ((struct command *)p2)->string);
}
void sort_commands() {
struct command commands[SHELL_COMMANDS];
for (int i = 0; i < shell_commands_len; ++i) {
commands[i].string = shell_commands[i];
commands[i].func = shell_pointers[i];
commands[i].desc = shell_descript[i];
}
qsort(&commands, shell_commands_len, sizeof(struct command), comp_shell_commands);
for (int i = 0; i < shell_commands_len; ++i) {
shell_commands[i] = commands[i].string;
shell_pointers[i] = commands[i].func;
shell_descript[i] = commands[i].desc;
}
}
void show_version(void) {
printf("esh 1.3.0\n");
}
void show_usage(int argc, char * argv[]) {
printf(
"Esh: The Experimental Shell\n"
"\n"
"usage: %s [-lha] [path]\n"
"\n"
" -c \033[4mcmd\033[0m \033[3mparse and execute cmd\033[0m\n"
//-c cmd \033[...
" -v \033[3mshow version information\033[0m\n"
" -? \033[3mshow this help text\033[0m\n"
"\n", argv[0]);
}
void add_path(void) {
char * envvar = getenv("PATH");
if (!envvar) {
add_path_contents("/bin");
return;
}
char * tmp = strdup(envvar);
do {
char * end = strstr(tmp,":");
if (end) {
*end = '\0';
end++;
}
add_path_contents(tmp);
tmp = end;
} while (tmp);
free(tmp);
}
int main(int argc, char ** argv) {
pid = getpid();
signal(SIGINT, sig_pass);
signal(SIGWINCH, sig_pass);
getuser();
gethost();
install_commands();
/* Parse $PATH to add contents */
add_path();
sort_commands();
if (argc > 1) {
int c;
while ((c = getopt(argc, argv, "c:v?")) != -1) {
switch (c) {
case 'c':
shell_interactive = 0;
last_ret = shell_exec(optarg, strlen(optarg), NULL);
return (last_ret == -1) ? 0 : last_ret;
case 'v':
show_version();
return 0;
case '?':
show_usage(argc, argv);
return 0;
}
}
}
if (optind < argc) {
shell_interactive = 2;
FILE * f = fopen(argv[optind],"r");
if (!f) {
fprintf(stderr, "%s: %s: %s\n", argv[0], argv[optind], strerror(errno));
return 1;
}
shell_argc = argc - 1;
shell_argv = &argv[1];
while (!feof(f)) {
char buf[LINE_LEN] = {0};
fgets(buf, LINE_LEN, f);
int ret = shell_exec(buf, LINE_LEN, f);
if (ret >= 0) last_ret = ret;
}
return 0;
}
shell_interactive = 1;
while (1) {
draw_prompt(last_ret);
char buffer[LINE_LEN] = {0};
read_entry(buffer);
int ret = shell_exec(buffer, LINE_LEN, stdin);
if (ret >= 0) last_ret = ret;
rline_scroll = 0;
}
return 0;
}
/*
* cd [path]
*/
uint32_t shell_cmd_cd(int argc, char * argv[]) {
if (argc > 1) {
if (chdir(argv[1])) {
goto cd_error;
} /* else success */
} else /* argc < 2 */ {
char * home = getenv("HOME");
if (home) {
if (chdir(home)) {
goto cd_error;
}
} else {
char home_path[512];
sprintf(home_path, "/home/%s", username);
if (chdir(home_path)) {
goto cd_error;
}
}
}
return 0;
cd_error:
fprintf(stderr, "%s: could not cd '%s': no such file or directory\n", argv[0], argv[1]);
return 1;
}
/*
* history
*/
uint32_t shell_cmd_history(int argc, char * argv[]) {
for (int i = 0; i < rline_history_count; ++i) {
printf("%d\t%s\n", i + 1, rline_history_get(i));
}
return 0;
}
uint32_t shell_cmd_export(int argc, char * argv[]) {
if (argc > 1) {
putenv(argv[1]);
}
return 0;
}
uint32_t shell_cmd_exit(int argc, char * argv[]) {
if (argc > 1) {
exit(atoi(argv[1]));
} else {
exit(0);
}
return -1;
}
uint32_t shell_cmd_help(int argc, char * argv[]) {
show_version();
printf("\nThis shell is not POSIX-compliant, please be careful.\n\n");
printf("Built-in commands:\n");
for (int i = 0; i < shell_commands_len; ++i) {
if (!shell_descript[i]) continue;
printf(" %-20s - %s\n", shell_commands[i], shell_descript[i]);
}
return 0;
}
void install_commands() {
shell_install_command("cd", shell_cmd_cd, "change directory");
shell_install_command("exit", shell_cmd_exit, "exit the shell");
shell_install_command("export", shell_cmd_export, "set environment variables");
shell_install_command("help", shell_cmd_help, "display this help text");
shell_install_command("history", shell_cmd_history, "list command history");
}
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