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Audit head(1)
1) Use (s)size_t in head(). 2) BUGFIX: only check buf[len - 1] when len > 0, else there would be an overflow when getline returns 0 (which can happen) and a very potential segmentation fault. 3) fix error-messages. 4) update usage(). 5) argv-argc-style. 6) clear up the main loop with if (newline). 7) add newline before return.
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b7c199e050
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38066de8c2
2
README
2
README
@ -35,7 +35,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
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= find yes none
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#* fold yes none
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=* grep yes none
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=* head yes none
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=*| head yes none
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=*| hostname non-posix none
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=* kill yes none
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=*| link yes none
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33
head.c
33
head.c
@ -6,27 +6,25 @@
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#include "util.h"
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static void
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head(FILE *fp, const char *str, long n)
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head(FILE *fp, const char *fname, size_t n)
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{
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char *buf = NULL;
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size_t size = 0;
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size_t i = 0, size = 0;
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ssize_t len;
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unsigned long i = 0;
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while (i < n && ((len = getline(&buf, &size, fp)) != -1)) {
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while (i < n && (len = getline(&buf, &size, fp)) >= 0) {
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fputs(buf, stdout);
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if (buf[len - 1] == '\n')
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i++;
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i += (len && (buf[len - 1] == '\n'));
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}
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free(buf);
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if (ferror(fp))
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eprintf("%s: read error:", str);
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eprintf("getline %s:", fname);
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}
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static void
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usage(void)
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{
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eprintf("usage: %s [-n lines] [-N] [file...]\n", argv0);
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eprintf("usage: %s [-n num] [-N] [file ...]\n", argv0);
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}
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int
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@ -34,8 +32,7 @@ main(int argc, char *argv[])
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{
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size_t n = 10;
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FILE *fp;
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int ret = 0;
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int newline, many;
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int ret = 0, newline, many;
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ARGBEGIN {
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case 'n':
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@ -48,23 +45,25 @@ main(int argc, char *argv[])
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usage();
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} ARGEND;
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if (argc == 0) {
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if (!argc) {
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head(stdin, "<stdin>", n);
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} else {
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many = argc > 1;
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for (newline = 0; argc > 0; argc--, argv++) {
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if (!(fp = fopen(argv[0], "r"))) {
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weprintf("fopen %s:", argv[0]);
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for (newline = 0; *argv; argc--, argv++) {
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if (!(fp = fopen(*argv, "r"))) {
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weprintf("fopen %s:", *argv);
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ret = 1;
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continue;
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}
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if (newline)
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putchar('\n');
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if (many)
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printf("%s==> %s <==\n",
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newline ? "\n" : "", argv[0]);
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printf("==> %s <==\n", *argv);
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newline = 1;
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head(fp, argv[0], n);
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head(fp, *argv, n);
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fclose(fp);
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}
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}
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return ret;
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}
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