Shell – Use piped stdin as argument to next command

argumentscommand lineshell

How do I use the output of a command as a parameter in another command? My specific example is that I want to get the PID of a process using pgrep and pass it to the -p option of lsof.

I've tried things like the following:

pgrep myprocess | lsof -p /dev/stdin
pgrep myprocess | lsof -p -

I know you can do it like this:

pid=$(pgrep myprocess) && lsof -p "$pid"

But there has to be a better way to do it. Perhaps xargs or something? I haven't been able to find something clean, so I'd appreciate any help.

Thanks!

Best Answer

Assuming that pgrep may return multiple PIDs:

$ pgrep mycommand | xargs -n 1 lsof -p

This will, for each PID, run lsof -p with the PID appended.

Related Solutions

Show contents of many files

The two standard commands head and tail print a header with the file name if you pass them more than one file argument. To print the whole file, use tail -n +1 (print from the first line onwards, i.e. everything).

Here, it looks like you want to see every file except the single one whose name begins with a dot. Dot files are “hidden” under unix: they don't appear in the default output of ls or in a wildcard match. So matching every non-hidden files is done with just *.

tail -n +1 *

(Strictly speaking, tail -n +1 -- * is needed in case one of the file names begins with a -.)

Shell – zsh tab completion on empty line

# expand-or-complete-or-list-files
function expand-or-complete-or-list-files() {
    if [[ $#BUFFER == 0 ]]; then
        BUFFER="ls "
        CURSOR=3
        zle list-choices
        zle backward-kill-word
    else
        zle expand-or-complete
    fi
}
zle -N expand-or-complete-or-list-files
# bind to tab
bindkey '^I' expand-or-complete-or-list-files

Best Answer

Related Solutions

Show contents of many files

Shell – zsh tab completion on empty line

Related Question