Bash basics

Bash certainly has its set of snafus.

• To 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

• To 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

• To check for an error

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

• To read input from user

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