Prevent cat from opening a binary file

Question

Is there a way to prevent or prompt you when trying to cat binary files?

Oftentimes I need to work with log files or data files, some of which are text and others not. It's easy to get mixed up, and accidentally trying to cat a binary file is annoying for obvious reasons.

Ideally I'd want an alias to cat that will prompt you if it detects a file is (with high probability) not plaintext.

Answer 1

I really don't think this is worth it when you could just check before cating something, but you could set up a function in your ~/.bashrc to do this:

cat(){
    for i in "$@"
    do
        if  file --mime "$i" | grep "charset=binary" >/dev/null 
        then
            printf "File %s is binary, skipping\n" "$i" >&2
        else
            /bin/cat "$i"
        fi
    done
}

That will run file to check if the file's mime-type is charset=binary and, if so, it will skip it. If that test fails, the file is not binary and /bin/cat is called. You can use it just like you would the regular cat:

$ cat /bin/bash /etc/os-release
File "/bin/bash" is binary, skipping
PRETTY_NAME="Linux Mint LMDE"
NAME="Linux Mint LMDE"
ID=linuxmint
ANSI_COLOR="1;31"

Answer 2

If you call file with -i it will return the mime type allowing you to determine if it is text or not.

file -i file.name | grep text/ && cat file.name

if file.name is binary the && does not execute the cat and if its plain text then it does.

This now matches script and other "text" files that are not marked as "plain"

Answer 3

In addition to what said here you can simply use less instead of cat.

It prompts if the file is not a regular one, and give some plus as, for example, the list of the files in a zip,rar archive...

By the way you can use even cat -v that will transform non reading characters without adding a $ to the end of each line.

Answer 4

Save this as a script for example newcat.sh, and make it executable:

#!/bin/bash
result=`file $1 | grep -c "binary"`
if [ "$result" -gt 0 ]
then
    echo "executable file"
else
        cat $1
fi

then use it as ./newcat.sh filename