msh/msh.c

#define _POSIX_C_SOURCE 200809l

#include <sys/types.h>

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <pwd.h>
#include <termios.h>

#include "config.h"
#include "fstr.h"
#include "err.h"

fstr_t PS1 = {0};
unsigned int histsize = DEF_HISTSIZE;

// Buffered user data
struct {
	char *name;
	char *home;
	uid_t uid;
	gid_t gid;
} uinfo = {0};

struct {
	// $ or #
	char tag;
} shinfo;

struct {
	struct termios tio;
	struct termios tio_before;
} terminfo;

void sh_setup_terminal(void);
void sh_update_uinfo(void);
void sh_update_shinfo(void);
void sh_update_ps1(void);
inline void sh_print_ps1(void);

int main(int argc, char **argv)
{
	(void)argc;
	(void)argv;
	char i;

	sh_setup_terminal();
	for (;;) {
		sh_update_uinfo();
		sh_update_shinfo();
		sh_update_ps1();
		sh_print_ps1();
		fflush(stdout);
		while (1) {
			read(STDIN_FILENO, &i, 1); // This blocks
			fputc(i, stdout);
			fflush(stdout);
			if (i == '\n')
				break;
		}
	}

	return EXIT_SUCCESS;
}

void sh_setup_terminal(void)
{
	if (tcgetattr(STDOUT_FILENO, &terminfo.tio_before) == -1)
		die("tcgetattr:");
	terminfo.tio = terminfo.tio_before;
	/* Do not echo and input is available immediately */
	terminfo.tio.c_lflag &= ~ECHO;
	terminfo.tio.c_lflag &= ~ICANON;
	if (tcsetattr(STDOUT_FILENO, TCSANOW, &terminfo.tio) == -1)
		die("tcsetattr:");
}

void sh_update_uinfo(void)
{
	struct passwd *pw;
	uid_t nuid;
	nuid = getuid();
	if (nuid == uinfo.uid && uinfo.name)
		return;
	uinfo.uid = nuid;
	pw = getpwuid(uinfo.uid);
	// User not found
	if (!pw)
		die("getpwuid:");
	uinfo.gid = pw->pw_gid;
	uinfo.name = estrdup(pw->pw_name);
	uinfo.home = estrdup(pw->pw_dir);
}

void sh_update_shinfo(void)
{
	shinfo.tag = uinfo.uid ? '$' : '#';
}

void sh_print_ps1(void)
{
	fputs(PS1.s, stdout);
}

void sh_update_ps1(void)
{
	fstr_clear(&PS1);
	fstr_append_char(&PS1, shinfo.tag);
	fstr_append_char(&PS1, ' ');
}