Bash basics

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Bash certainly has its set of snafus.

proper way to exit mid-script

kill -SIGINT $$;

store commands in variables

# NOTE don't put spaces around equals sign!
# NOTE don't use ampersands within command strings, they won't work
# use a blank command if needed, that's fine
mycmd1="command param param"
mycmd2="cmd2 param"
if [ -e /myspecialplace ]
mycmd2=""
fi
mycmd3="cmd3 param"
$mycmd1 && $mycmd2 && $mycmd3

capture output

myout=`program1 param`;
  • Note the difference a single quote makes to output...
$ eval echo "abc   def"
abc def
$ eval 'echo "abc   def"'
abc   def

check for an error

mkdir "$d2"
if [ $? -gt 0 ]; then
   echo "mkdir error, try that again..."
   exit 3
fi

read input from user

echo "Create the subdirectory?  [$d2]"
if read answer; then
    if [ ${answer} = "y" ] || [ ${answer} = "yes" ]; then
        {whatever}
    else
        {whatever}
    fi
fi

grep your code

I use an alias for common params, so just do this:

grep "my[ ]regex" source/code/directory/ --include="*.cpp"

You can also use (and tweak) this helper:

cd src
grepcode blah

Here's the alias:

alias grep='grep -inIEr --color=ALWAYS'

powerful grep options

misc

bash chmod dirs
find /path/to/base/dir -type d -exec chmod g+x {} \;