Linux – bash commands that don’t fit on one page – make output scrollable

bashlinux

Probably been answered somewhere, but its difficult to frame the search phrase.

I am running a bash terminal window and some commands are too big to fit on the page (e.g. ps -A)

I vaguely recall a command line parameter / method that shows the command output page by page so I can scroll through the output, but I can't recall what it is…. any pointers?

Best Answer

  • For commands I use often, I generally set up a function in my .bashrc to make them paginate if longer than a screen.

    Like your example: (ps -A)

    function ps { command ps "$@" |& less -F; }
    

    This replaces ps with a function, named ps, which calls the original ps command with whatever arguments given on the command line, then pipes the output (stdout and stderr, using the |& pipe) into less -F, which pauses if there's more than a screen-full, but exits immediately if it's less than a screen-full.

    VERY handy, doesn't interfere with anything I've worked with so far, and is just cool!

    You can even add oft-used options into the command/functions too:

    function nm { command nm --demangle "$@" |& less -F; }
    

    This makes nm always demangle C++ symbols. AND paginates the output. Yay!

    I'm running Debian, so I use the apt-cache command quite often, search and show mostly. This function causes those particular options to paginate, search output is sorted, and everything paginates:

    function apt-cache { case  "$1" in "search") command apt-cache "$@" | sort | less -F;; *) command apt-cache "$@" | less -F;; esac; }
    

    If the command is 'search', sort the output, then paginate with less -F, but if command is anything else, just paginate, without sorting.

    Occasionally I forget I've got the functions, and I'll do something like:

    apt-cache search gcc | less
    

    The function doesn't interfere, everything works as expected, no harm either way.

    Another little tweak, I use the same .bashrc on all my systems, so sometimes a utility might not be installed, so there's no need for the function. I make them conditional like this:

    which apt-cache &>/dev/null && function apt-cache { case  "$1" in "search") command apt-cache "$@" |& sort | less -F;; *) command apt-cache "$@" |& less -F;; esac; }
    

    This just uses the which command to determine if a program is available, if it isn't, it quietly fails and skips installing the function. Taa Daa!

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