Linux – Difference between xargs /bin/ls and exec ls

findlinuxmacosxargs

Hi this may be a very newbie question, but why doesnt the xargs /bin/ls work in this case? I thought it was supposed to be faster? Also what are those /fd/3 directories?

sh-3.2# find / -name 'GOALS*' -exec ls -l {} \;
find: /dev/fd/3: Not a directory
find: /dev/fd/4: Not a directory
.... This returns me the expected result....

However this returns the whole list of files in the directory

sh-3.2# find / -name GOALS* -type f | xargs /bin/ls -l

I am on a MacOS.

Best Answer

you need to quote the * in the second find command,
the /dev/fd/* are devices which corresponds with stdin, stdout, stderr etc. thouse devices are simlinked and are different for each process,
the -type f says, the result has to be regular file, thus the /dev/fd/* are not in the result as they are block devices,
the xargs ls -l does the same as your ls -l {}... I even doubt the better performance in this case, but xargs is smarter and there are reasons to use it, eg. correct handling of files with whitespaces inside it,

If you are debugging the second version of your find, first of all see the output w/o the | xargs ls -l part

Related Solutions

Linux Bash – How to Perform Multistep Conditional Actions with find and exec

; is the shell's command separator. Everything after it will be a separate command and won't be passed to find, since command parsing is done before execution. Likewise, &>/dev/null applies to the entire find command, not just to php, regardless of where it is located (before, in the middle, or after).

To use such operators in your -exec or -ok, you will have to explicitly call a shell:

find ... -exec bash -c 'php -l "{}" >&/dev/null; echo $?' \;

Note that the special characters are inside quotes, which means they will be passed literally to find and then to bash.

This is less simple but might be more reliable with "weird" filenames:

find ... -exec bash -c 'php -l "$1" >&/dev/null; echo $?' -- {} \;

This will display the results in a more readable form: (this is entirely about bash scripting now, not about find anymore)

find ... -exec bash -c '
    if php -l "$1" >&/dev/null; then
        echo "$1: pass"
    else
        echo "$1: fail"
    fi' -- {} \;

Using awk with find -exec

You could try without find, if all you want is all the files. While in data/all/, run this:

for file in ./*; do awk '{print$2}' "$file" > "../pos/$(basename $file)"; done

If you want to cover the files in the whole hierarchy under /data/all, you can enable the globstar option if you are using bash (I believe this would "just work" on zsh) and then use ** to match all files:

shopt -s globstar
for file in ./**; do awk '{print$2}' "$file" > "../pos/$(basename $file)"; done

Best Answer

Related Solutions

Linux Bash – How to Perform Multistep Conditional Actions with find and exec

Using awk with find -exec

Related Question