128 lines
2.7 KiB
C
128 lines
2.7 KiB
C
/*
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* Copyright (c) 2016 Nicholas De Nova.
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*
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* Permission to use, copy, modify, and/or 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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* readlink.c
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* Print symbolic link target.
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*/
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#include <err.h>
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#include <errno.h>
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#include <stdbool.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 <unistd.h>
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static void compact_arguments(int* argc, char*** argv)
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{
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for ( int i = 0; i < *argc; i++ )
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{
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while ( i < *argc && !(*argv)[i] )
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{
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for ( int n = i; n < *argc; n++ )
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(*argv)[n] = (*argv)[n+1];
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(*argc)--;
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}
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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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bool append_newline = true;
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bool canonicalize = false;
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for ( int i = 1; i < argc; i++ )
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{
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const char* arg = argv[i];
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if ( arg[0] != '-' || !arg[1] )
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continue;
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argv[i] = NULL;
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if ( !strcmp(arg, "--") )
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break;
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if ( arg[1] != '-' )
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{
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char c;
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while ( (c = *++arg) )
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switch ( c )
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{
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case 'f': canonicalize = true; break;
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case 'n': append_newline = false; break;
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default:
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errx(1, "unknown option -- '%c'", c);
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}
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}
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else if ( !strcmp(arg, "--canonicalize") )
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canonicalize = true;
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else if ( !strcmp(arg, "--no-newline") )
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append_newline = false;
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else
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errx(1, "unknown option: %s", arg);
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}
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compact_arguments(&argc, &argv);
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if ( argc < 2 )
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errx(1, "missing path operand");
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else if ( argc > 2 )
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errx(1, "unexpected extra operand");
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char* buffer;
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if ( canonicalize )
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{
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buffer = realpath(argv[1], NULL);
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if ( !buffer )
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err(1, "%s", argv[1]);
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}
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else
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{
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size_t buffer_size = 4096;
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while ( true )
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{
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buffer = malloc(buffer_size);
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if ( !buffer )
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err(1, "malloc");
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ssize_t path_size = readlink(argv[1], buffer, buffer_size);
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if ( path_size < 0 )
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err(1, "%s", argv[1]);
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if ( (size_t) path_size == buffer_size )
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{
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free(buffer);
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if ( SIZE_MAX / 2 < buffer_size )
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{
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errno = ENOMEM;
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err(1, "malloc");
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return 1;
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}
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buffer_size *= 2;
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continue;
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}
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buffer[path_size] = '\0';
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break;
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}
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}
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fputs(buffer, stdout);
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if ( append_newline )
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putchar('\n');
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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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