stupid for loop examples

stupid.sh

# rename some files based on some counter

x=0  # set an environment variable for our counter
for i in foo/*  # for every file in the foo directory
do
    # we're going to rename the file, and prefix it with the value in the
    # counter. the variable $i will contain both the directory foo, as well as
    # the filename (e.g., foo/bar). Since we want to prefix the number on to
    # the filename, we need to somehow strip out the foo/ part. we can do this
    # using a program called basename (it's worth a peak at its man page).
    # basename can be used to get just the filename from a path. the syntax is
    # janky, but you can have things get executed inline if you put it
    # inbetween parentheses with a dollar sign to tell the computer to treat it
    # as magical gold. there's also a few ways in which the variables are being
    # referred too here, sometimes its ${thing}, or $thing. the use of curly
    # braces just make it explicit, and avoid cases of ambiguity that might
    # confuse the computer (remember, the computer is stupid).
    mv $i foo/${x}_$(basename $i)

    # in order to increment our little counter, we need to use let. its annoying.
    let x=$x+1
done


# woooo... awesome fun party time. now lets grep stuff and do things with the
# stuff.

# also, hyperbolie and a half is an amazing comic. necessary meme:
# http://imgur.com/4EjMcKR
for thing in `/bin/ls | grep m | rev`  # grep things with m, and reverse them
do
    echo $thing
done


# do a whole lot of something
for f1 in `seq 1 5`
do
    for f2 in {a,b,c,d}
    do
        echo $f1 $2
    done
done


# say you have access to a giant super computer. and say you don't like the other users and want to submit a large number of jobs. yes.
for some_file in ls foo/*
do
    # this is specific somewhat to torque based clusters
    echo "your_awesome_program --some-argument -i ${some_file}" | qsub -N "w00t"
done