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substr.c
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substr.c
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/*
* Copyright (c) 2014 Tristan Le Guern <[email protected]>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#ifdef NEED_LIBBSD
# include <bsd/stdlib.h>
#endif
void usage(void);
int
main(int argc, char *argv[]) {
unsigned int pos;
unsigned int length;
size_t slen;
char ch;
char *string;
const char *errstr;
while ((ch = getopt(argc, argv, "")) != -1)
switch (ch) {
default:
usage();
/* NOTREACHED */
}
argc -= optind;
argv += optind;
if (argc < 2 || argc > 3 || argv[0] == NULL) {
usage();
/* NOTREACHED */
}
string = argv[0];
slen = strlen(string);
pos = strtonum(argv[1], 1, slen, &errstr);
if (errstr)
errx(1, "pos is %s", errstr);
if (argc == 2) {
length = slen - pos + 1;
} else {
length = strtonum(argv[2], 1, slen - pos + 1, &errstr);
if (errstr)
errx(1, "length is %s", errstr);
}
string = string + pos - 1;
string[length] = '\0';
(void)printf("%s\n", string);
return 0;
}
void
usage(void) {
(void)fprintf(stderr, "usage: %s string pos length\n", getprogname());
exit(1);
}