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Kevin |
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/*
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* esh - the 'extensible' shell.
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*
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* Utility functions for system calls.
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*
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* Developed by Godmar Back for CS 3214 Fall 2009
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* Virginia Tech.
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*/
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#include <termios.h>
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#include <stdio.h>
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#include <errno.h>
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#include <string.h>
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#include <stdarg.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include <signal.h>
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#include <assert.h>
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#include "esh-sys-utils.h"
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static const char rcsid [] = "$Id: esh-sys-utils.c,v 1.4 2011/01/21 20:13:06 cs3214 Exp $";
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/* Utility function for esh_sys_fatal_error and esh_sys_error */
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static void
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vesh_sys_error(char *fmt, va_list ap)
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{
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char errmsg[1024];
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strerror_r(errno, errmsg, sizeof errmsg);
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vfprintf(stderr, fmt, ap);
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fprintf(stderr, "%s\n", errmsg);
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}
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/* Print information about the last syscall error */
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void
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esh_sys_error(char *fmt, ...)
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{
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va_list ap;
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va_start(ap, fmt);
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vesh_sys_error(fmt, ap);
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va_end(ap);
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}
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/* Print information about the last syscall error and then exit */
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void
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esh_sys_fatal_error(char *fmt, ...)
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{
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va_list ap;
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va_start(ap, fmt);
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vesh_sys_error(fmt, ap);
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va_end(ap);
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exit(EXIT_FAILURE);
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}
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static int terminal_fd = -1; /* the controlling terminal */
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static struct termios saved_tty_state; /* the state of the terminal when shell
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was started. */
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/* Initialize tty support. Return pointer to saved initial terminal state */
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struct termios *
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esh_sys_tty_init(void)
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{
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char *tty;
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assert(terminal_fd == -1 || !!!"esh_sys_tty_init already called");
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terminal_fd = open(tty = ctermid(NULL), O_RDWR);
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if (terminal_fd == -1)
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esh_sys_fatal_error("opening controlling terminal %s failed: ", tty);
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esh_sys_tty_save(&saved_tty_state);
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return &saved_tty_state;
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}
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/* Save current terminal settings.
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* This function is used when a job is suspended.*/
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void
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esh_sys_tty_save(struct termios *saved_tty_state)
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{
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int rc = tcgetattr(terminal_fd, saved_tty_state);
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if (rc == -1)
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esh_sys_fatal_error("tcgetattr failed: ");
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}
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/* Restore terminal to saved settings.
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* This function is used when resuming a suspended job. */
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void
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esh_sys_tty_restore(struct termios *saved_tty_state)
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{
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int rc = tcsetattr(terminal_fd, TCSADRAIN, saved_tty_state);
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if (rc == -1)
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esh_sys_fatal_error("could not restore tty attributes tcsetattr: ");
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}
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/* Get a file descriptor that refers to controlling terminal */
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int
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esh_sys_tty_getfd(void)
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{
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assert(terminal_fd != -1 || !!!"esh_sys_tty_init() must be called");
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return terminal_fd;
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}
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/* Return true if this signal is blocked */
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bool
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esh_signal_is_blocked(int sig)
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{
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sigset_t mask;
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if (sigprocmask(0, NULL, &mask) == -1)
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esh_sys_error("sigprocmask failed while retrieving current mask");
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return sigismember(&mask, sig);
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}
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/* Helper for esh_signal_block and esh_signal_unblock */
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static bool
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__mask_signal(int sig, int how)
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{
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sigset_t mask, omask;
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sigemptyset(&mask);
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sigaddset(&mask, sig);
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if (sigprocmask(how, &mask, &omask) != 0)
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esh_sys_error("sigprocmask failed for %d/%d", sig, how);
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return sigismember(&omask, sig);
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}
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/* Block a signal. Returns true it was blocked before */
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bool
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esh_signal_block(int sig)
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{
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return __mask_signal(sig, SIG_BLOCK);
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}
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/* Unblock a signal. Returns true it was blocked before */
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bool
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esh_signal_unblock(int sig)
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{
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return __mask_signal(sig, SIG_UNBLOCK);
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}
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/* Install signal handler for signal 'sig' */
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void
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esh_signal_sethandler(int sig, sa_sigaction_t handler)
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{
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sigset_t emptymask;
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sigemptyset(&emptymask);
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struct sigaction sa = {
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.sa_sigaction = handler,
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/* do not block any additional signals (besides 'sig') when
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* signal handler is entered. */
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.sa_mask = emptymask,
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/* restart system calls when possible */
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.sa_flags = SA_RESTART | SA_SIGINFO
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};
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if (sigaction(sig, &sa, NULL) != 0)
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esh_sys_fatal_error("sigaction failed for signal %d", sig);
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}
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