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#!/bin/bash

echo '          ${var-_}   ${var:-_}  $var       ${!var[@]}'

test_all()
{
    test "${var-_}" && echo -n 'T          ' || echo -n 'F          '
    test "${var:-_}" && echo -n 'T          ' || echo -n 'F          '
    test "$var" && echo -n 'T          ' || echo -n 'F          '
    [[ "${!var[@]}" ]] && echo 'T' || echo 'F'

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#!/bin/bash
# by Dennis Williamson
# 2010-10-06, revised 2010-11-10
# for http://stackoverflow.com/questions/3869072/test-for-non-zero-length-string-in-bash-n-var-or-var
# designed to fit an 80 character terminal

dw=5    # description column width
w=6     # table column width

t () { printf "%-${w}s" "true"; }

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tar -X <(cat /etc/fstab | cut -d ' ' -f 2 | grep ^$dir) -zcvf dir.tar.gz $dir/*

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#!/bin/bash
# Filenames can contain *any* character except only null (\0) and slash (/);
# here's some general rules to handle them:
#
# $'...' can be used to create human readable strings with escape sequences.
#
# ' -- ' in commands is necessary to separate arguments from filenames, since
# filenames can start with '--', and would therefore be handled as parameters.
# To handle parameters properly (like GNU tools) use `getopt`.
#

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# This works even with really weird filenames like $'--$`\! *@ \a\b\e\E\f\n\r\t\v\\\"\' '
file_count()
{
    if [ ! -e "$1" ]
    then
        exit 1
    fi

    local -i files=$(find "$(readlink -f -- "$1")" -type f -print0 | grep -cz -- -)
    echo $files

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# Can be used to for example count the number of files returned by `find ... -print0`
grep -cz . -- -

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grep -v '^\(none\|rootfs\)' /proc/mounts > /etc/mtab

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command | tee /dev/fd/2

# Can be used to debug variable computations - Just plonk the tee at the end:
# $ uid=$(id -u | tee /dev/fd/2)
# 1234
# $ echo $uid
# 1234

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while true
do
    inotifywait -e modify,attrib,move,delete .
    make test
done

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find . -maxdepth 1 -print0 | \
sort --zero-terminated | \
while IFS= read -rd $'\0' path
do
    grep "$(basename -- "${path:2}")" -- Makefile >/dev/null || echo "Could not find $path"
done