3
\$\begingroup\$

This shell script writes my environment variables. If there is an argument, the shell script will grep for the argument in the environment variables.

PAGER=more
if type less > /dev/null;then PAGER=less; fi
echo $PAGER
if [ -z ${1+x} ]; then printenv|"$PAGER"; else printenv|grep "$1"|"$PAGER"; fi

If the above script is correct then I will work on my shell to be able to parse it. It can parse everything except the last line, which I added today.

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3
+50
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Readability

Just because Bash let's you cram a lot of statements on a single line doesn't mean you should. I recommend to split this up to multiple lines, and also to put spaces around |, like this:

#!/bin/bash

PAGER=more
if less >/dev/null; then
    PAGER=less
fi
echo $PAGER

if [ -z ${1+x} ]; then
    printenv | "$PAGER"
else
    printenv | grep "$1" | "$PAGER"
fi

But if you like compact writing style, a reasonable compromise is to replace the first if statement with an alternative writing style using && like this:

less >/dev/null && PAGER=less

Error handling

I'm not sure if it's intentional, but if the less command doesn't exist (but in most systems it does), this line will emit an error message:

if type less >/dev/null

To avoid errors, you want to suppress stderr too in addition to stdout:

if type less >/dev/null 2>&1

Prefer simple solutions

This is hacky, cryptic:

if [ -z ${1+x} ]; then

I suggest a much more readable, simple equivalent:

if [ -z "$1" ]; then

Don't repeat yourself

The printenv command is repeated in both branches of the last if statement. You could move it in front of the if, like this:

printenv | \
if [ -z "$1" ]; then
    "$PAGER"
else
    grep "$1" | "$PAGER"
fi

However, in this writing style it's important that the \ on the line before the if is the last character on the line directly in front of the line break.

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