Bash – When the lines of a file or directory get too long, upgrade to ls list format

bashbashrccoreutils

Is there a way I can do this? For example if a gets a long name like:

i-have-names-that-are-too-long-to-describe/
i-have-names-that-are-too-long-to-describe-2/
i-have-names-that-are-too-long-to-descri-3/

Can I "upgrade" over from ls to ls -l given that I have a name of a file or directory that is longer than than say, 20 characters?

Is there a way to set up a bash function in my .bashrc to do this? I'll call the resulting function lls().

@tripleee asked:

Do you want ls -l when the input file name is long? Why? It will make the output longer, not shorter. What if you receive a mix of long and short filenames?

I want it more so that reading the long filenames are systematized to a list (and easier for me to digest and read going down a fixed column); for a mix of long and short filenames, I would default to the list format.

Best Answer

There's no builtin option in ls that does what you want. You'd have to parse the output then restart if "long" filenames are found, or do something like:

$ ls ??????????* >& /dev/null && ls -l || ls

(Put as many ? as your length limit. You can set that up as an alias.)

Why don't you simply use ls -1? (That's a one, not a lowercase L.) It always lists files in a single column. (Or pipe ls to more or less, which also goes to single column display.) Or use find with -maxdepth 1.

Related Solutions

Bash – Identify Files with Non-ASCII or Non-Printable Characters

Assuming that "foreign" means "not an ASCII character", then you can use find with a pattern to find all files not having printable ASCII characters in their names:

LC_ALL=C find . -name '*[! -~]*'

(The space is the first printable character listed on http://www.asciitable.com/, ~ is the last.)

The hint for LC_ALL=C is required (actually, LC_CTYPE=C and LC_COLLATE=C), otherwise the character range is interpreted incorrectly. See also the manual page glob(7). Since LC_ALL=C causes find to interpret strings as ASCII, it will print multi-byte characters (such as π) as question marks. To fix this, pipe to some program (e.g. cat) or redirect to file.

Instead of specifying character ranges, [:print:] can also be used to select "printable characters". Be sure to set the C locale or you get quite (seemingly) arbitrary behavior.

Example:

$ touch $(printf '\u03c0') "$(printf 'x\ty')"
$ ls -F
dir/  foo  foo.c  xrestop-0.4/  xrestop-0.4.tar.gz  π
$ find -name '*[! -~]*'       # this is broken (LC_COLLATE=en_US.UTF-8)
./x?y
./dir
./π
... (a lot more)
./foo.c
$ LC_ALL=C find . -name '*[! -~]*'
./x?y
./??
$ LC_ALL=C find . -name '*[! -~]*' | cat
./x y
./π
$ LC_ALL=C find . -name '*[![:print:]]*' | cat
./x y
./π

Bash – Compact Bash Prompt for Directory Tree and Filename

First of all, you might simply want to change the \w with \W. That way, only the name of the current directory is printed and not its entire path:

terdon@oregano:/home/mydirectory1/second_directory_with_a_too_long_name/my_actual_directory_with_another_long_name $ PS1="\u@\h:\W \$ "
terdon@oregano:my_actual_directory_with_another_long_name $

That might still not be enough if the directory name itself is too long. In that case, you can use the PROMPT_COMMAND variable for this. This is a special bash variable whose value is executed as a command before each prompt is shown. So, if you set that to a function that sets your desired prompt based upon the length of your current directory's path, you can get the effect you're after. For example, add these lines to your ~/.bashrc:

get_PS1(){
        limit=${1:-20}
        if [[ "${#PWD}" -gt "$limit" ]]; then
                ## Take the first 5 characters of the path
                left="${PWD:0:5}"
                ## ${#PWD} is the length of $PWD. Get the last $limit
                ##  characters of $PWD.
                right="${PWD:$((${#PWD}-$limit)):${#PWD}}"
                PS1="\[\033[01;33m\]\u@\h\[\033[01;34m\] ${left}...${right} \$\[\033[00m\] "
        else
                PS1="\[\033[01;33m\]\u@\h\[\033[01;34m\] \w \$\[\033[00m\] "
        fi


}
PROMPT_COMMAND=get_PS1

The effect looks like this:

terdon@oregano ~ $ cd /home/mydirectory1/second_directory_with_a_too_long_name/my_actual_directory_with_another_long_name
terdon@oregano /home...th_another_long_name $

Best Answer

Related Solutions

Bash – Identify Files with Non-ASCII or Non-Printable Characters

Bash – Compact Bash Prompt for Directory Tree and Filename

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