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Groups > comp.lang.c > #395764
| From | James Kuyper <jameskuyper@alumni.caltech.edu> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: is_binary_file() |
| Date | 2025-12-10 12:46 -0500 |
| Organization | A noiseless patient Spider |
| Message-ID | <10hcbls$1b254$1@dont-email.me> (permalink) |
| References | <10gvvh8$1vv6e$1@dont-email.me> <10h01k8$1ta3h$1@dont-email.me> <10h02nm$1ta3h$2@dont-email.me> <10hbluk$1fc0e$1@dont-email.me> |
On 2025-12-10 06:35, Michael Sanders wrote:
...
> #include <stdio.h> // FILE, fopen, fread, fclose
> #include <stddef.h> // size_t
>
> // is_text_file()
> // Returns:
> // -1 : could not open file
> // 0 : is NOT a text file (binary indicators found)
> // 1 : is PROBABLY a text file (no strong binary signatures)
>
> int is_text_file(const char *path) {
> // Try opening the file in binary mode,
> // required so that bytes are read exact.
> FILE *f = fopen(path, "rb");
> if (!f) return -1; // Could not open file
>
> unsigned char buf[4096]; // 4KB chunks
> size_t n, i;
>
> // Read in file until EOF
> while ((n = fread(buf, 1, sizeof(buf), f)) > 0) {
> for (i = 0; i < n; i++) {
> unsigned char c = buf[i];
I'd recommend against buffering this; C stdio is already buffered, and
it just complicates your code to keep track of a second level of
buffering. Use getc() instead.
> // 1. null byte is a very strong indication of binary data.
> // Text files virtually never contain 0x00.
> if (c == 0x00) {
> fclose(f);
> return 0; // Contains binary-only byte: NOT text
> }
>
> // 2. Check for raw C0 control codes (0x01–0x1F).
> // We *allow* \t (09), \n (0A), \r (0D) because they are normal in text.
> // Any other control code is highly suspicious and usually means binary.
> if (c < 0x20) {
> if (c != 0x09 && c != 0x0A && c != 0x0D) {
> fclose(f);
> return 0; // unexpected control character → NOT text
> }
> }
I would recommend against use of explicit numerical codes for
characters. They make your code dependent upon a particular encoding,
and you're free to make that choice, but for implementations where that
encoding is the default, the corresponding C escape sequences will have
precisely the the correct value, and make it easier to understand what
your code is doing:
0x00 '\0'
0x09 '\t'
0x0A '\n'
0x0D '\r'
0x20 ' '
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is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-06 01:05 +0000
Re: is_binary_file() Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2025-12-06 01:41 +0000
Re: is_binary_file() Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2025-12-06 02:00 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-08 17:40 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-10 11:35 +0000
Re: is_binary_file() scott@slp53.sl.home (Scott Lurndal) - 2025-12-10 15:07 +0000
Re: is_binary_file() Michael S <already5chosen@yahoo.com> - 2025-12-10 19:00 +0200
Re: is_binary_file() scott@slp53.sl.home (Scott Lurndal) - 2025-12-10 17:18 +0000
Re: is_binary_file() Richard Heathfield <rjh@cpax.org.uk> - 2025-12-10 19:42 +0000
Re: is_binary_file() bart <bc@freeuk.com> - 2025-12-10 22:37 +0000
Re: is_binary_file() Paul <nospam@needed.invalid> - 2025-12-10 22:35 -0500
Re: is_binary_file() bart <bc@freeuk.com> - 2025-12-11 11:46 +0000
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-11 12:53 +0100
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-10 18:42 +0000
Re: is_binary_file() Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2025-12-10 15:58 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-10 18:44 +0000
Re: is_binary_file() James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-12-10 12:46 -0500
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-10 18:45 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-10 18:41 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-10 20:57 +0000
Re: is_binary_file() scott@slp53.sl.home (Scott Lurndal) - 2025-12-10 22:07 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-11 01:09 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-11 12:33 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-12 19:25 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-12 22:54 +0000
Re: is_binary_file() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-12-12 15:33 -0800
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-13 00:20 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-13 02:32 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-16 00:26 +0000
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-16 17:24 +0100
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-17 03:19 +0000
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-17 07:57 +0100
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-17 19:35 +0000
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-18 08:44 +0100
Re: is_binary_file() bart <bc@freeuk.com> - 2025-12-18 12:49 +0000
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-18 14:06 +0100
Re: is_binary_file() gazelle@shell.xmission.com (Kenny McCormack) - 2025-12-18 13:17 +0000
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-18 16:03 +0100
Re: is_binary_file() Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-12-05 17:42 -0800
Re: is_binary_file() scott@slp53.sl.home (Scott Lurndal) - 2025-12-06 17:37 +0000
Re: is_binary_file() Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-12-06 16:05 -0800
Re: is_binary_file() Louis Krupp <lkrupp@invalid.pssw.com.invalid> - 2025-12-07 03:43 -0700
Re: is_binary_file() scott@slp53.sl.home (Scott Lurndal) - 2025-12-07 16:47 +0000
Re: is_binary_file() Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-12-27 03:18 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-08 17:46 +0000
Re: is_binary_file() Kaz Kylheku <046-301-5902@kylheku.com> - 2025-12-06 02:42 +0000
Re: is_binary_file() bart <bc@freeuk.com> - 2025-12-06 12:42 +0000
Re: is_binary_file() scott@slp53.sl.home (Scott Lurndal) - 2025-12-06 17:40 +0000
Re: is_binary_file() Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2025-12-06 18:04 +0000
Re: is_binary_file() scott@slp53.sl.home (Scott Lurndal) - 2025-12-06 19:06 +0000
Re: is_binary_file() Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2025-12-06 21:16 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-08 17:48 +0000
Re: is_binary_file() Kaz Kylheku <046-301-5902@kylheku.com> - 2025-12-08 19:26 +0000
Re: is_binary_file() Richard Heathfield <rjh@cpax.org.uk> - 2025-12-08 19:42 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-09 21:49 +0000
Re: is_binary_file() Paul <nospam@needed.invalid> - 2025-12-06 03:14 -0500
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-08 17:56 +0000
Re: is_binary_file() scott@slp53.sl.home (Scott Lurndal) - 2025-12-08 20:16 +0000
Re: is_binary_file() David Brown <david.brown@hesbynett.no> - 2025-12-09 09:03 +0100
Re: is_binary_file() Richard Heathfield <rjh@cpax.org.uk> - 2025-12-09 09:43 +0000
Re: is_binary_file() Richard Harnden <richard.nospam@gmail.invalid> - 2025-12-09 10:17 +0000
Re: is_binary_file() Kaz Kylheku <046-301-5902@kylheku.com> - 2025-12-09 20:15 +0000
Re: is_binary_file() tTh <tth@none.invalid> - 2025-12-09 12:22 +0100
Re: is_binary_file() Paul <nospam@needed.invalid> - 2025-12-09 20:26 -0500
Re: is_binary_file() Paul <nospam@needed.invalid> - 2025-12-09 06:38 -0500
Re: is_binary_file() Michael S <already5chosen@yahoo.com> - 2025-12-09 17:31 +0200
Re: is_binary_file() Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-12-28 02:49 +0000
Re: is_binary_file() Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-12-28 00:12 +0000
Re: is_binary_file() richard@cogsci.ed.ac.uk (Richard Tobin) - 2025-12-28 00:43 +0000
Re: is_binary_file() scott@slp53.sl.home (Scott Lurndal) - 2025-12-06 17:33 +0000
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-07 19:04 +0100
Re: is_binary_file() James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-12-06 20:37 -0500
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-08 18:02 +0000
Re: is_binary_file() James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-12-09 16:29 -0500
Re: is_binary_file() Michael S <already5chosen@yahoo.com> - 2025-12-10 11:21 +0200
Re: is_binary_file() James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-12-10 12:48 -0500
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-10 11:38 +0000
Re: is_binary_file() antispam@fricas.org (Waldek Hebisch) - 2025-12-07 03:43 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-08 18:04 +0000
Re: is_binary_file() bart <bc@freeuk.com> - 2025-12-08 18:44 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-09 19:53 +0000
Re: is_binary_file() Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-12-09 15:42 -0800
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-10 11:41 +0000
Re: is_binary_file() Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-12-10 15:20 -0800
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-10 23:59 +0000
Re: is_binary_file() James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-12-09 16:23 -0500
Re: is_binary_file() Richard Harnden <richard.nospam@gmail.invalid> - 2025-12-07 19:01 +0000
Re: is_binary_file() Richard Heathfield <rjh@cpax.org.uk> - 2025-12-07 21:51 +0000
Re: is_binary_file() Richard Harnden <richard.nospam@gmail.invalid> - 2025-12-07 22:49 +0000
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-08 13:51 +0100
Re: is_binary_file() scott@slp53.sl.home (Scott Lurndal) - 2025-12-08 16:04 +0000
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-08 19:27 +0100
Re: is_binary_file() Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-12-27 05:51 +0000
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-29 16:06 +0100
Re: is_binary_file() mjos_examine <m6502x64@gmail.com> - 2025-12-29 11:49 -0500
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-29 20:49 +0100
Re: is_binary_file() Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-12-30 01:52 +0000
Re: is_binary_file() scott@slp53.sl.home (Scott Lurndal) - 2025-12-08 16:02 +0000
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-08 18:07 +0000
Re: is_binary_file() Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-12-27 03:13 +0000
Re: is_binary_file() Paul <nospam@needed.invalid> - 2025-12-27 01:28 -0500
Re: is_binary_file() Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-12-27 21:27 +0000
Re: is_binary_file() antispam@fricas.org (Waldek Hebisch) - 2025-12-28 05:46 +0000
Re: is_binary_file() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-12-07 14:42 -0800
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-08 18:09 +0000
Re: is_binary_file() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-12-09 12:45 -0800
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-08 20:36 +0100
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-08 20:50 +0100
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-09 15:09 +0100
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-10 09:18 +0100
Re: is_binary_file() Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-12-08 14:43 -0800
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-09 21:38 +0000
Re: is_binary_file() Kaz Kylheku <046-301-5902@kylheku.com> - 2025-12-11 17:33 +0000
Re: is_binary_file() Bonita Montero <Bonita.Montero@gmail.com> - 2025-12-11 19:10 +0100
Re: is_binary_file() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-12-11 14:56 -0800
Re: is_binary_file() James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-12-11 18:15 -0500
Re: is_binary_file() Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-12-12 02:19 +0100
Re: is_binary_file() Michael Sanders <porkchop@invalid.foo> - 2025-12-14 08:27 +0000
Re: is_binary_file() Lynn McGuire <lynnmcguire5@gmail.com> - 2025-12-17 00:52 -0600
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