Import peek(1) from trinity/src
This commit is contained in:
159
src/peek.c
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159
src/peek.c
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/*
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* Copyright (c) 2023–2024 DTB <trinity@trinity.moe>
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* SPDX-License-Identifier: AGPL-3.0-or-later
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*
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* This program is free software: you can redistribute it and/or modify it under
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* the terms of the GNU Affero General Public License as published by the Free
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* Software Foundation, either version 3 of the License, or (at your option) any
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* later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
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* details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see https://www.gnu.org/licenses/.
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*/
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#include <signal.h> /* sigaction(2), signal(2), struct sigaction, SIGINT */
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#include <stdio.h> /* fclose(3), fdopen(3), fprintf(3), getc(3), perror(3),
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* putc(3), stderr, stdin, stdout, EOF, NULL */
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#include <stdlib.h> /* exit(3), size_t, EXIT_FAILURE */
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#include <string.h> /* strerror(3) */
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#if !defined EX_OK || !defined EX_OSERR || !defined EX_USAGE
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# include <sysexits.h>
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#endif
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#include <termios.h> /* tcgetattr(3), tcsetattr(3), struct termios, ECHO */
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#include <unistd.h> /* dup(2), execvp(3), fork(2), getopt(3), isatty(3),
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* pipe(2), STDIN_FILENO */
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static int oserr(char *s){ perror(s); return EX_OSERR; }
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static char *program_name = "peek";
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static int usage(char *s){
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fprintf(stderr, "Usage: %s (-1enot) (-p [program [arguments...]])\n",
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s == NULL ? program_name : s);
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return EX_USAGE;
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}
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/* Restores terminal echo; otherwise when a user ^Cs the terminal would
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* continue to not display typed text. If sig isn't zero, this will terminate
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* the program. */
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void restore_echo(int sig){
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static struct termios t;
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tcgetattr(STDIN_FILENO, &t);
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t.c_lflag |= ECHO;
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tcsetattr(STDIN_FILENO, TCSAFLUSH, &t);
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if(sig != 0)
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exit(EXIT_FAILURE);
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else
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return;
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}
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int main(int argc, char *argv[]){
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int eof;
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char include_eof;
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FILE *outputs[] = {
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NULL /* stdout */,
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NULL /* stderr */,
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NULL /* -p */
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};
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int p[2] = {0, 0};
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if(argc < 1)
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usage(argv[0]);
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eof = EOF;
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include_eof = 0;
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{ /* options parsing */
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int c;
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while((c = getopt(argc, argv, "1enopt")) != -1)
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switch(c){
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case '1': eof = '\n'; break;
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case 'n': include_eof = 1; break;
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case 'o': outputs[0] = stdout; break;
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case 'e': outputs[1] = stderr; break;
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case 'p':
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if(pipe(p) != 0 || (outputs[2] = fdopen(p[1], "ab")) == NULL)
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return oserr(argv[0]);
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break;
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case 't':
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if(isatty(STDIN_FILENO) != 1){
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fprintf(stderr, "%s: Must be run in a terminal"
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" (option -t specified)\n", argv[0]);
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return EX_USAGE;
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}
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default: return usage(argv[0]);
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}
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}
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/* If -p is used there must be additional arguments. getopt(3) wouldn't
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* work for this because optarg would have to be one string to give to
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* system(3) or an equivalent and it would be a mess of parsing and
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* security issues. Any intended usage works with this slightly funkier
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* argument parsing, unintended usages work as happy coincidence. */
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if((argc > optind) == (outputs[2] == 0))
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return usage(argv[0]);
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if(outputs[2] != 0)
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switch(fork()){
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case 0:
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if(close(p[1]) == 0 && dup2(p[0], STDIN_FILENO) == STDIN_FILENO)
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execvp(argv[optind], &argv[optind]);
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case -1:
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return oserr(argv[0]);
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default:
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if(close(p[0]) != 0)
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return oserr(argv[0]);
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}
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{ /* install signal handler */
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/* There isn't a difference in functionality between the signal(2) and
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* sigaction(2) methods. sigaction(2) is vastly preferred for
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* portability but some configurations can only use signal(2). */
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/* Errors aren't terminating because the worst that happens is some
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* terminal phooeyness if things go awry. */
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#if defined _POSIX_C_SOURCE
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struct sigaction act = { 0 };
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act.sa_handler = restore_echo;
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if(sigaction(SIGINT, &act, NULL) != 0)
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perror(argv[0]);
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#else
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if(signal(SIGINT, restore_echo) == SIG_ERR)
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perror(argv[0]);
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#endif
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}
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{ /* banish terminal echo */
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struct termios t;
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tcgetattr(STDIN_FILENO, &t);
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t.c_lflag ^= ECHO;
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tcsetattr(STDIN_FILENO, TCSAFLUSH, &t);
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}
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{ /* actual input loop */
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int c;
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size_t i;
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do{ if((c = getc(stdin)) != eof || include_eof)
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for(i = 0; i < (sizeof outputs)/(sizeof *outputs); ++i)
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if(outputs[i] != NULL && putc(c, outputs[i]) == EOF){
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perror(argv[0]);
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if(outputs[i] != stdout && outputs[i] != stderr)
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fclose(outputs[i]);
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outputs[i] = NULL;
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}
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}while(c != eof);
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}
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restore_echo(0);
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return EX_OK;
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}
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