Bash: using function with pipe as argument for another function

Question

I'm trying to make function-wrapper for another functions to distinguish its in terminal

red_line="$(tput setaf 1)## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## $(tput sgr 0)"

function wrapper {
    echo $red_line;
    echo "$(tput setaf 1)## $(tput setab 7)$(tput setaf 0)$1 $(tput sgr 0)";
    $2;
    echo $red_line;
}

function foo {
    wrapper "custom command description" "ps axo pid,stat,pcpu,comm | tail -n 10;"
}

but error was occurred: ps: illegal argument: |

I've tried to use $(ps ... | tail -n 10) and backticks instead of string and then print out result in wrapper with echo $2, but caught another errors

Also tried "eval $(ps ... | tail -n 10)" and it also didn't work.

Everything works just fine w/o wrapper:

function pss {
    echo $red_line
    echo "$(tput setaf 1)## $(tput setab 7)$(tput setaf 0)formatted 'ps ax' command $(tput sgr 0)"

    ps axo pid,stat,pcpu,comm | tail -n $1;

    echo $red_line
}

result screenshot

I'm trying to put a command in a variable, but the complex cases always fail! — chepner
– chepner, Commented Oct 12, 2016 at 11:40

aiven · Accepted Answer · 2016-10-12 12:52:45Z

1

Tnx @chepner for referring post about passing complex commands as argument. But the actual problem was with mess with double quotes in functions arguments in echo and wrapper.

Correct code:

red_line="$(tput setaf 1)## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## $(tput sgr 0)"

function wrapper {
    echo $red_line;
    echo "$(tput setaf 1)## $(tput setab 7)$(tput setaf 0)$1 $(tput sgr 0)";
    echo "$2";
    echo $red_line;
}

function pss {
    res="$(ps axo pid,stat,pcpu,comm | tail -n $1)"
    wrapper "custom command description" "$res"
    # also work: 
    # wrapper "custom command description" "$(ps axo pid,stat,pcpu,comm | tail -n $1)"
}

answered Oct 12, 2016 at 12:52

aiven

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Comments

Mathieu J. · Accepted Answer · 2016-10-13 12:23:08Z

1

Aiven Lebowski 's answer is correct. but if you really wanted to keep foo as-is and execute $2 in place where you put it, you only needed to do eval

red_line="$(tput setaf 1)## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## $(tput sgr 0)"

function wrapper {
    echo $red_line;
    echo "$(tput setaf 1)## $(tput setab 7)$(tput setaf 0)$1 $(tput sgr 0)";
    eval $2
    echo $red_line;
}

function foo {
    wrapper "custom command description" "ps axo pid,stat,pcpu,comm | tail -n 10;"
}

I hope this helps

answered Oct 13, 2016 at 12:23

Mathieu J.

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