How to check if the file is a binary file and read all the files which are not?

Question

How can I know if a file is a binary file?

For example, compiled c file.

I want to read all files from some directory, but I want ignore binary files.

Answer 1

Perhaps this would suffice ..

if ! file /path/to/file | grep -iq ASCII ; then
    echo "Binary"
fi

if file /path/to/file | grep -iq ASCII ; then
    echo "Text file"
fi

Answer 2

It's kind of brute force to exclude binary files with tr -d "[[:print:]\n\t]" < file | wc -c, but it is no heuristic guesswork either.

find . -type f -maxdepth 1 -exec /bin/sh -c '
   for file in "$@"; do
      if [ $(LC_ALL=C LANG=C tr -d "[[:print:]\n\t]" < "$file" | wc -c) -gt 0 ]; then
         echo "${file} is no ASCII text file (UNIX)"
      else
         echo "${file} is ASCII text file (UNIX)"
      fi
   done
' _ '{}' +

The following brute-force approach using grep -a -m 1 $'[^[:print:]\t]' file seems quite a bit faster, though.

find . -type f -maxdepth 1 -exec /bin/sh -c '
   tab="$(printf "\t")"
   for file in "$@"; do
      if LC_ALL=C LANG=C grep -a -m 1 "[^[:print:]${tab}]" "$file" 1>/dev/null 2>&1; then
         echo "${file} is no ASCII text file (UNIX)"
      else
         echo "${file} is ASCII text file (UNIX)"
      fi
   done
' _ '{}' + 

Answer 3

Adapted from excluding binary file

find . -exec file {} \; | grep text | cut -d: -f1

Answer 4

BSD grep

Here is a simple solution to check for a single file using BSD grep (on macOS/Unix):

grep -q "\x00" file && echo Binary || echo Text

which basically checks if file consist NUL character.

Using this method, to read all non-binary files recursively using find utility you can do:

find . -type f -exec sh -c 'grep -q "\x00" {} || cat {}' ";"

Or even simpler using just grep:

grep -rv "\x00" .

For just current folder, use:

grep -v "\x00" *

Unfortunately the above examples won't work for GNU grep, however there is a workaround.

GNU grep

Since GNU grep is ignoring NULL characters, it's possible to check for other non-ASCII characters like:

$ grep -P "[^\x00-\x7F]" file && echo Binary || echo Text

^{Note: It won't work for files containing only NULL characters.}

Answer 5

cat+grep

Assuming binary means the file containing NULL characters, this shell command can help:

(cat -v file.bin | grep -q "\^@") && echo Binary || echo Text

or:

grep -q "\^@" <(cat -v file.bin) && echo Binary

This is the workaround for grep -q "\x00", which works for BSD grep, but not for GNU version.

Basically -v for cat converts all non-printing characters so they are visible in form of control characters, for example:

$ printf "\x00\x00" | hexdump -C
00000000  00 00                                             |..|
$ printf "\x00\x00" | cat -v
^@^@
$ printf "\x00\x00" | cat -v | hexdump -C
00000000  5e 40 5e 40                                       |^@^@|

where ^@ characters represent NULL character. So once these control characters are found, we assume the file is binary.

---

The disadvantage of above method is that it could generate false positives when characters are not representing control characters. For example:

$ printf "\x00\x00^@^@" | cat -v | hexdump -C
00000000  5e 40 5e 40 5e 40 5e 40                           |^@^@^@^@|

See also: How do I grep for all non-ASCII characters.

Answer 6

perl -E 'exit((-B $ARGV[0])?0:1);' file-to-test

Could be used to check whenever "file-to-test" is binary. The above command will exit wit code 0 on binary files, otherwise the exit code would be 1.

The reverse check for text file can look like the following command:

perl -E 'exit((-T $ARGV[0])?0:1);' file-to-test

Likewise the above command will exit with status 0 if the "file-to-test" is text (not binary).

Read more about the -B and -T checks using command perldoc -f -X.