Linux System Administration

Useful Elements for bash Scripts

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echo "$0 ran at" $(date) >> delete.log

if [ ! -e "$1" ]

then

echo "$1 does not exist" >> delete.log

elif [ -f "$1" ]

then

echo -n "file $1 " >> delete.log

if rm "$1" 2>> delete-err.log

then

echo "deleted" >> delete.log

else

echo "not deleted" >> delete.log

fi

elif [ -d "$1" ]

then

echo -n "directory $1 " >> delete.log

if rmdir "$1" 2>> delete-err.log

then

echo "deleted" >> delete.log

else

echo "not deleted" >> delete.log

fi

fi

Now, at last, when you run the command:

admin@server1:~$ ./removefiles "my file"

the last line of delete.log will be:

file my file deleted

Loops

If you want to do something more than once, you need a loop. bash has three fla-

vors:

for, while, and until.

The lovely and talented

for loop has this general appearance:

for arg in list

do

commands

done

It executes the commands action (which can cover as many lines and separate com-

mands as you want) specified between

do and done for each item in list. When the

commands run, they can access the current item from

list through the variable $arg,

The syntax may be a bit confusing at first: in the

for statement you must specify arg

without the dollar sign, but in the commands you must specify $arg with the dollar

sign.

Some simple examples are:

admin@server1:~$ for stooge in moe larry curly

> do

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Chapter 10: ...