File: teletype.c 1 /* 2 The MIT License (MIT) 3 4 Copyright © 2020-2025 pacman64 5 6 Permission is hereby granted, free of charge, to any person obtaining a copy of 7 this software and associated documentation files (the “Software”), to deal 8 in the Software without restriction, including without limitation the rights to 9 use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies 10 of the Software, and to permit persons to whom the Software is furnished to do 11 so, subject to the following conditions: 12 13 The above copyright notice and this permission notice shall be included in all 14 copies or substantial portions of the Software. 15 16 THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 17 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 18 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 19 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 20 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 21 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 22 SOFTWARE. 23 */ 24 25 /* 26 You can build this command-line app by running 27 28 cc -Wall -s -O2 -o ./teletype ./teletype.c 29 */ 30 31 #include <stdbool.h> 32 #include <stdio.h> 33 #include <string.h> 34 #include <time.h> 35 36 #ifdef _WIN32 37 #include <windows.h> 38 #endif 39 40 // info is the multi-line help message 41 const char* info = "" 42 "teletype [options...] [filenames...]\n" 43 "\n" 44 "Simulate the cadence of old-fashioned teletype machines by delaying output.\n" 45 "\n" 46 "\n" 47 "Options\n" 48 "\n" 49 " -h, --h show this help message\n" 50 " -help, --help aliases for option -h\n" 51 ""; 52 53 // handle_reader shows all bytes read from the source given as colored hex 54 // values, showing offsets and ASCII symbols on the sides of each output line 55 void handle_reader(FILE* w, FILE* src) { 56 struct timespec delay; 57 delay.tv_sec = 0; 58 delay.tv_nsec = 0; 59 60 while (!feof(w)) { 61 int c = getc(src); 62 if (c < 0) { 63 break; 64 } 65 66 delay.tv_nsec = (c == '\n') ? 750 * 1e6 : 15 * 1e6; 67 nanosleep(&delay, NULL); 68 putc(c, w); 69 } 70 } 71 72 // handle_file handles data from the filename given; returns false only when 73 // the file can't be opened 74 bool handle_file(FILE* w, const char* path) { 75 FILE* f = fopen(path, "rb"); 76 if (f == NULL) { 77 // ensure currently-buffered/deferred output shows up right now: not 78 // doing so may scramble results in the common case where stdout and 79 // stderr are the same, thus confusing users 80 putc('\n', w); 81 82 fprintf(stderr, "\x1b[31mcan't open file named %s\x1b[0m\n", path); 83 return false; 84 } 85 86 handle_reader(w, f); 87 fclose(f); 88 return true; 89 } 90 91 // is_help_option simplifies control-flow for func run 92 bool is_help_option(char* s) { 93 return (s[0] == '-') && ( 94 strcmp(s, "-h") == 0 || strcmp(s, "-help") == 0 || 95 strcmp(s, "--h") == 0 || strcmp(s, "--help") == 0 96 ); 97 } 98 99 // run returns the number of errors 100 int run(int argc, char** argv, FILE* w) { 101 size_t files = 0; 102 size_t errors = 0; 103 104 // handle all filenames/options given 105 for (size_t i = 1; i < argc && !feof(w); i++) { 106 // a `-` filename stands for the standard input 107 if (argv[i][0] == '-' && argv[i][1] == 0) { 108 handle_reader(w, stdin); 109 continue; 110 } 111 112 if (is_help_option(argv[i])) { 113 // help option quits the app right away 114 fprintf(stderr, "%s", info); 115 return 0; 116 } 117 118 if (!handle_file(w, argv[i])) { 119 errors++; 120 } 121 files++; 122 } 123 124 // no filenames means use stdin as the only input 125 if (files == 0) { 126 handle_reader(w, stdin); 127 } 128 129 return errors; 130 } 131 132 int main(int argc, char** argv) { 133 #ifdef _WIN32 134 setmode(fileno(stdin), O_BINARY); 135 // ensure output lines end in LF instead of CRLF on windows 136 setmode(fileno(stdout), O_BINARY); 137 setmode(fileno(stderr), O_BINARY); 138 #endif 139 140 // disable buffering for stdout 141 setvbuf(stdout, NULL, _IONBF, 0); 142 143 return run(argc, argv, stdout) == 0 ? 0 : 1; 144 }