2 * ASCII magic -- file types that we know based on keywords
3 * that can appear anywhere in the file.
5 * Copyright (c) Ian F. Darwin, 1987.
6 * Written by Ian F. Darwin.
8 * This software is not subject to any license of the American Telephone
9 * and Telegraph Company or of the Regents of the University of California.
11 * Permission is granted to anyone to use this software for any purpose on
12 * any computer system, and to alter it and redistribute it freely, subject
13 * to the following restrictions:
15 * 1. The author is not responsible for the consequences of use of this
16 * software, no matter how awful, even if they arise from flaws in it.
18 * 2. The origin of this software must not be misrepresented, either by
19 * explicit claim or by omission. Since few users ever read sources,
20 * credits must appear in the documentation.
22 * 3. Altered versions must be plainly marked as such, and must not be
23 * misrepresented as being the original software. Since few users
24 * ever read sources, credits must appear in the documentation.
26 * 4. This notice may not be removed or altered.
30 static const char rcsid[] =
39 /* an optimisation over plain strcmp() */
40 #define STREQ(a, b) (*(a) == *(b) && strcmp((a), (b)) == 0)
45 int nbytes; /* size actually read */
47 int i, has_escapes = 0;
49 char nbuf[HOWMANY+1]; /* one extra for terminating '\0' */
51 register struct names *p;
54 * Do the tar test first, because if the first file in the tar
55 * archive starts with a dot, we can confuse it with an nroff file.
57 switch (is_tar(buf, nbytes)) {
59 ckfputs("tar archive", stdout);
62 ckfputs("POSIX tar archive", stdout);
67 * for troff, look for . + letter + letter or .\";
68 * this must be done to disambiguate tar archives' ./file
69 * and other trash from real troff input.
72 unsigned char *tp = buf + 1;
74 while (isascii(*tp) && isspace(*tp))
75 ++tp; /* skip leading whitespace */
76 if ((isascii(*tp) && (isalnum(*tp) || *tp=='\\') &&
77 isascii(tp[1]) && (isalnum(tp[1]) || tp[1] == '"'))) {
78 ckfputs("troff or preprocessor input text", stdout);
82 if ((*buf == 'c' || *buf == 'C') &&
83 isascii(buf[1]) && isspace(buf[1])) {
84 ckfputs("fortran program text", stdout);
89 /* Make sure we are dealing with ascii text before looking for tokens */
90 for (i = 0; i < nbytes - 1; i++) {
91 if (!isascii(buf[i]) ||
92 (iscntrl(buf[i]) && !isspace(buf[i]) &&
93 buf[i] != '\b' && buf[i] != '\032' && buf[i] != '\033'
96 return 0; /* not all ASCII */
99 /* look for tokens from names.h - this is expensive! */
100 /* make a copy of the buffer here because strtok() will destroy it */
101 s = strcpy(nbuf, buf);
102 has_escapes = (strchr(s, '\033') != NULL);
103 while ((token = strtok(s, " \t\n\r\f")) != NULL) {
104 s = NULL; /* make strtok() keep on tokin' */
105 for (p = names; p < names + NNAMES; p++) {
106 if (STREQ(p->name, token)) {
107 ckfputs(types[p->type], stdout);
109 ckfputs(" (with escape sequences)",
116 /* all else fails, but it is ASCII... */
117 ckfputs("ASCII text", stdout);
119 ckfputs(" (with escape sequences)", stdout);