Piping a file list for another shell command

Being a student again takes a longer while than I expected to get used to, which gives me a long hiatus in my posting, but also puts me in a different and stimulating environment.

This post was inspired by a question from my colleague, who want to first find some file entries and then merge them into a file, so the initial attempt was:

After getting the list of file names , it might be tempting to pipe this result to cat and then to a text file like:

But this is only giving you the list of file names in merged.txt because it is actually ./c.txt\n./b.txt\n./a.txt (\n is the new-line character) being piped to cat. Though cat does try to find a file matching this name, there is obviously none in this directory, and cat has no other choice but printing the string it receives as it is.

I am bad at terminal commands, so the first thing I came up with was to use awk to send the file names one by one to cat with system(), which makes a system call in awk scripts.

This worked, but the use of awk seemed like an overkill.

I later noticed xargs, which takes standard input, splits it by blanks or new lines and sends the resulting list to a command. This looked like exactly the thing I wanted.

Indeed, find . -regex “./[a-z].txt" | xargs cat >> "merged.txt" does exactly the same thing in a more elegant way. Additionally, xargs is of course more versatile than that.

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