Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
Example 10−22. Continuing at a higher loop level
#!/bin/bash
# The "continue N" command, continuing at the Nth level loop.
for outer in I II III IV V
do
echo; echo −n "Group $outer: "
# outer loop
for inner in 1 2 3 4 5 6 7 8 9 10 # inner loop
do
if [ "$inner" −eq 7 ]
then
continue 2 # Continue at loop on 2nd level, that is "outer loop".
# Replace above line with a simple "continue"
# to see normal loop behavior.
fi
echo −n "$inner " # 8 9 10 will never echo.
done
done
echo; echo
# Exercise:
# Come up with a meaningful use for "continue N" in a script.
exit 0
Example 10−23. Using "continue N" in an actual task
# Albert Reiner gives an example of how to use "continue N":
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
# Suppose I have a large number of jobs that need to be run, with
#+ any data that is to be treated in files of a given name pattern in a
#+ directory. There are several machines that access this directory, and
#+ I want to distribute the work over these different boxen. Then I
#+ usually nohup something like the following on every box:
while true
do
for n in .iso.*
do
[ "$n" = ".iso.opts" ] && continue
beta=${n#.iso.}
[ −r .Iso.$beta ] && continue
[ −r .lock.$beta ] && sleep 10 && continue
lockfile −r0 .lock.$beta || continue
echo −n "$beta: " `date`
run−isotherm $beta
date
ls −alF .Iso.$beta
[ −r .Iso.$beta ] && rm −f .lock.$beta
continue 2
done
break
Chapter 10. Loops and Branches 116