mirror of
https://gitlab.com/sortix/sortix.git
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92 lines
2.5 KiB
C
92 lines
2.5 KiB
C
/*
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* Copyright (c) 2013, 2021 Jonas 'Sortie' Termansen.
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* Copyright (c) 2022 Juhani 'nortti' Krekelä.
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* Copyright (c) 2022 Dennis Wölfing.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* date.c
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* Print or set system date and time.
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*/
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#include <err.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#include <unistd.h>
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// Note: There's no way to discern whether the format string was too long for
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// the output buffer or if the output was simply empty, so don't call this
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// function with a format that could produce an empty string. E.g. use a prefix
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// like '+' and skip it when using the string.
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static char* astrftime(const char* format, const struct tm* tm)
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{
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size_t format_size = strlen(format) + 1;
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size_t buffer_size = format_size;
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while ( true )
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{
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char* buffer = calloc(buffer_size, 2);
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if ( !buffer )
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return NULL;
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buffer_size *= 2;
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if ( strftime(buffer, buffer_size, format, tm) )
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return buffer;
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free(buffer);
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}
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}
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int main(int argc, char* argv[])
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{
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const char* format = "+%a %b %e %H:%M:%S %Z %Y";
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int opt;
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while ( (opt = getopt(argc, argv, "u")) != -1 )
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{
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switch ( opt )
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{
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case 'u':
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if ( setenv("TZ", "UTC0", 1) )
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err(1, "setenv");
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break;
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default: return 1;
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}
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}
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if ( 1 <= argc - optind )
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{
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if ( argv[optind][0] != '+' )
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errx(1, "setting the system time is not implemented");
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format = argv[optind];
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}
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if ( 2 <= argc - optind )
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errx(1, "unexpected extra operand: %s", argv[optind + 1]);
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time_t current_time = time(NULL);
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struct tm tm;
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if ( !localtime_r(¤t_time, &tm) )
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err(1, "localtime_r(%ji)", (intmax_t) current_time);
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char* string = astrftime(format, &tm);
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if ( !string )
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err(1, "malloc");
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if ( printf("%s\n", string + 1) == EOF )
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err(1, "stdout");
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free(string);
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if ( ferror(stdout) || fflush(stdout) == EOF )
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err(1, "stdout");
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return 0;
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}
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