commit 0ad3175e4c38d0f54fcce53cdda76a627b454cf7
parent 1d8dbdc5e8bbf040748d63f59aa4f54aa2dc59bd
Author: Claudio Alessi <smoppy@gmail.com>
Date: Tue, 7 Jan 2020 13:27:43 +0100
Add gsh.
Diffstat:
| A | gsh.c | | | 376 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
1 file changed, 376 insertions(+), 0 deletions(-)
diff --git a/gsh.c b/gsh.c
@@ -0,0 +1,376 @@
+/* Simple shell written in C.
+ * Compile with: cc -std=c99 -pedantic -Wall -O0 -o gsh gsh.c -lreadline */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <err.h>
+#include <errno.h>
+#include <signal.h>
+#include <wordexp.h>
+#include <sys/wait.h>
+#include <pwd.h>
+
+/* Avoid some NetBSD obscure build time warning */
+#if defined(__NetBSD__)
+# define _FUNCTION_DEF
+# define USE_VARARGS
+# define PREFER_STDARG
+#endif
+
+#include <readline/readline.h>
+#include <readline/history.h>
+
+#ifdef PATH_MAX
+static int pathmax = PATH_MAX;
+#else
+static int pathmax = 0;
+#endif
+#define PATH_MAX_GUESS 1024
+
+#define SH_NAME "gsh"
+#define SH_VERSION "0.01"
+
+typedef struct {
+ const char *name;
+ void (*func)(int argc, char *argv[]);
+ const char *desc;
+ const char *args;
+} keyword;
+
+/* globals */
+typedef void builtin(int, char *[]);
+builtin
+ do_exit,
+ do_echo,
+ do_putenv,
+ do_setenv,
+ do_unsetenv,
+ do_getenv,
+ do_help,
+ do_cd
+;
+static const keyword tblkeys[] = {
+ /* Command, Function, Description, Arguments */
+ { "exit", do_exit, "Exit from the shell", "[exit code]" },
+ { "echo", do_echo, "Show a message", "[message]" },
+ { "putenv", do_putenv, "Set the enviroment given variable(s)", "<variable>=<value> [...]" },
+ { "setenv", do_setenv, "Set an environment variable", "<variable> <value>" },
+ { "unsetenv", do_unsetenv, "Unset the environment given variable(s)", "<variable> [...]" },
+ { "getenv", do_getenv, "Print the value of the given environment variable(s)", "<variable> [...]" },
+ { "cd", do_cd, "Change the current working directory", "[pathname | -]" },
+ { "help", do_help, "Show this help", "[command]" },
+ { NULL, NULL, NULL, NULL }
+};
+
+/* function declarations */
+int sh_init(void);
+int run_cmd(int argc, char *argv[]);
+int run_key(int argc, char *argv[]);
+void remove_comment(char *p);
+void hdr_sigint(int sig);
+void cmdhelp(const char *cmd, int descr);
+void sigint_handler(int signum);
+void execute_command(char *command);
+char *strip_spaces(char *string);
+char *path_alloc(size_t *size);
+
+/* function implementations */
+void
+remove_comment(char *p) {
+ register int i = 0;
+ while(p[i] && p[i] != '#')
+ ++i;
+ if(p[i])
+ p[i] = '\0';
+}
+
+void
+cmdhelp(const char *cmd, int descr) {
+ int i;
+ for(i = 0; tblkeys[i].name; i++) {
+ if(!strncmp(tblkeys[i].name, cmd, strlen(tblkeys[i].name))) {
+ if(descr)
+ printf("%s\n", tblkeys[i].desc);
+ printf("Usage: %s %s\n", tblkeys[i].name, tblkeys[i].args);
+ break;
+ }
+ }
+ if(!tblkeys[i].name)
+ warnx("%s: unknown command", cmd);
+}
+
+char *
+strip_spaces(char *string) {
+ char *s, *e;
+ for(s = string; *s == ' ' && *s; s++)
+ ;
+ if(!*s)
+ return s;
+ for(e = s + strlen(s) - 1; *e == ' '; e--)
+ ;
+ *(e + 1) = '\0';
+ return s;
+}
+
+char *
+path_alloc(size_t *size) {
+ char *ptr;
+ if(!pathmax) {
+ errno = 0;
+ if((pathmax = pathconf("/", _PC_PATH_MAX)) < 0) {
+ if(!errno)
+ pathmax = PATH_MAX_GUESS;
+ else
+ warnx("pathconf caused error while reading _PC_PATH_MAX");
+ }
+ else
+ ++pathmax;
+ }
+ if((ptr = malloc(pathmax + 1)) == NULL)
+ warnx("cannot allocate the pathname");
+ if(size != NULL)
+ *size = pathmax + 1;
+ return(ptr);
+}
+void
+do_exit(int argc, char *argv[]) {
+ if(argc > 2) {
+ cmdhelp(argv[0], 0);
+ return;
+ }
+ exit((argv && argv[1] ? atoi(argv[1]) : EXIT_SUCCESS));
+}
+
+void
+do_echo(int argc, char *argv[]) {
+ int i = 0;
+ while(argv[++i]) {
+ printf("%s", argv[i]);
+ if(i == argc)
+ break;
+ printf(" ");
+ }
+ printf("\n");
+}
+
+void
+do_putenv(int argc, char *argv[]) {
+ size_t envsz;
+ int i;
+ char *envstr;
+ if(argc == 1) {
+ cmdhelp(argv[0], 0);
+ return;
+ }
+ for(i = 0; i < argc; i++) {
+ envsz = strlen(argv[i]) + 1;
+ if((envstr = malloc(envsz)) == NULL)
+ return;
+ strncpy(envstr, argv[i], envsz);
+ if(putenv(envstr))
+ free(envstr);
+ }
+}
+
+void
+do_setenv(int argc, char *argv[]) {
+ if(argc != 3) {
+ cmdhelp(argv[0], 0);
+ return;
+ }
+ setenv(argv[1], argv[2], 1);
+}
+
+void
+do_unsetenv(int argc, char *argv[]) {
+ if(argc == 1) {
+ cmdhelp(argv[0], 0);
+ return;
+ }
+ while( --argc && ! unsetenv(argv[argc]) )
+ ;
+}
+
+void
+do_getenv(int argc, char *argv[]) {
+ int i;
+ if(argc == 1) {
+ cmdhelp(argv[0], 0);
+ return;
+ }
+ for(i = 1; i < argc; i++)
+ printf("%s\n", getenv(argv[i]));
+}
+
+void
+do_cd(int argc, char *argv[]) {
+ struct passwd *pwd;
+ size_t tplen;
+ char *tp, *path;
+ if(argc > 2) {
+ cmdhelp(argv[0], 0);
+ return;
+ }
+ if(!(path = argv[1])) {
+ if(!(path = getenv("HOME"))) {
+ if((pwd = getpwuid(getuid())) != NULL)
+ path = pwd->pw_dir;
+
+ else {
+ /* This should never happen */
+ warnx("%s: cannot get the user home directory", argv[0]);
+ return;
+ }
+ }
+ }
+ if(*path == '-' && !path[1]) {
+ if(!(path = getenv("OLDPWD")))
+ return;
+ printf("%s\n", path); /* TODO: An option should toggle this call */
+ }
+ tp = path_alloc(&tplen);
+ getcwd(tp, tplen);
+ if(chdir(path)) {
+ warn("cd: %s", path);
+ return;
+ }
+ setenv("OLDPWD", tp, 1);
+}
+
+void
+do_help(int argc, char *argv[]) {
+ int i;
+ if(argc >= 2) {
+ cmdhelp(argv[1], argc == 2);
+ return;
+ }
+ printf("\n%s v.%s\n\n", SH_NAME, SH_VERSION);
+ for(i = 0; tblkeys[i].name; i++)
+ printf(" %-9s%s\n", tblkeys[i].name, tblkeys[i].desc);
+ printf("\n");
+}
+
+int
+run_key(int argc, char *argv[]) {
+ register int i;
+ for(i = 0; tblkeys[i].name; i++) {
+ if(!strncmp(tblkeys[i].name, argv[0], strlen(tblkeys[i].name))) {
+ tblkeys[i].func(argc, argv);
+ return 0;
+ }
+ }
+ return 1;
+}
+
+int
+run_cmd(int argc, char *argv[]) {
+ register pid_t pid;
+ if((pid = fork()) == -1)
+ return -1;
+ else if(pid == 0) {
+ execvp(argv[0], argv);
+
+ /* Exit status
+ * 126: The program is not executable
+ * 127: The program was not found
+ * 1: any other error */
+ if(errno == ENOENT)
+ errx(127, "%s: command not found", argv[0]);
+ else
+ err((errno == EACCES ? 126 : 1), "%s", argv[0]);
+ }
+ else {
+ while(waitpid(pid, NULL, 0) == -1) {
+ if(errno != EINTR)
+ return -1;
+ }
+ }
+ return 0;
+}
+
+/* XXX clean things up here */
+void
+sigint_handler(int signum) {
+ char *p;
+ if(!*(p = strip_spaces(rl_line_buffer)))
+ return;
+ add_history(p); /* Store it anyway */
+ *rl_line_buffer = '\0'; /* Clear the buffer */
+ rl_point =rl_end = 0; /* Reset the offsets */
+ rl_redisplay(); /* Update the line */
+ printf("(interrupt)\n"); /* Show a message */
+ rl_initialize(); /* (Re)Initialize the state */
+ rl_redisplay(); /* Update the line */
+}
+
+int
+sh_init() {
+ signal(SIGINT, sigint_handler);
+ signal(SIGTSTP, SIG_IGN);
+ signal(SIGQUIT, SIG_IGN);
+
+ putenv((char *)"PS1=$ ");
+ putenv((char *)"IFS= \n\t");
+
+ /* Set the default PATH, if unset (LFS 1.2) */
+ if(!getenv("PATH"))
+ putenv((char *)"PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin");
+
+ /* XXX startup file? */
+
+ return 0;
+}
+
+void
+execute_command(char *command) {
+ wordexp_t wordv;
+ register int wordc, wret;
+ if((wret = wordexp(command, &wordv, 0))) {
+ switch(wret) {
+ case WRDE_BADCHAR:
+ warnx("illegal character");
+ break;
+ case WRDE_NOSPACE:
+ warnx("out of memory");
+ break;
+ case WRDE_SYNTAX:
+ warnx("syntax error");
+ break;
+ }
+
+ return;
+ }
+ if(!wordv.we_wordv[0]) {
+ wordfree(&wordv);
+ return;
+ }
+ for(wordc = 0; wordv.we_wordv[wordc]; wordc++)
+ ;
+ if(run_key(wordc, wordv.we_wordv)) {
+ if(run_cmd(wordc, wordv.we_wordv))
+ warn("run_cmd");
+ }
+ wordfree(&wordv);
+}
+
+int
+main(void) {
+ char *buf, *p;
+ if(sh_init())
+ return 1;
+ while(1) {
+ if((buf = readline(getenv("PS1"))) == NULL)
+ break;
+ remove_comment(p);
+ if(*(p = strip_spaces(buf))) {
+ add_history(p);
+ execute_command(p);
+ }
+ free(buf);
+ }
+ printf("\n");
+ return 0;
+}
