Suppress output based on variable

Question

I have a script with an optional verbosity argument. Depending on its value I want to suppress output (pushd in example below, but in reality other, mostly git commands). Example:

verb=1
# pushd optionally outputs path (works but too long)
if [ $verb ]; then
  pushd ..
else
  pushd .. > /dev/null
fi
popd > /dev/null  # the same if.. would be needed here

What I am looking for is something along:

push .. $cond  # single line, outputing somehow controlled directly
popd $cond     # ditto

Anybody can help? Thanks,

Hans-Peter

choroba · Accepted Answer · 2013-03-15 12:13:04Z

2

You can redirect the output to a function whose definition depends on the $verb:

#! /bin/bash

verb=$1

if [[ $verb ]] ; then
    verb () {
        cat
    }
else
    verb () {
        :     # Does nothing.
    }
fi

echo A | verb

answered Mar 15, 2013 at 12:13

choroba

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Comments

cdarke · Accepted Answer · 2013-03-15 12:20:48Z

1

Use a different file descritor to redirect to:

if (( $verb ))
then
    exec 3>&1
else
    exec 3>/dev/null
fi

push .. >&3
popd >&3

This way, the condition is only tested once, at the beginning, rather then every time you do redirection.

answered Mar 15, 2013 at 12:20

cdarke

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