TECHPULP | Bash shell script to convert string from lower to upper case and vice versa

December 05, 2008

By: Neo

In Category Bash

The “tr” command can be used to convert a string variable to upper or lower case. The following function in a bash script converts first argument to lower case.

Convert the given argument into an all lower case string.

toLower() {
echo $1 | tr "[:upper:]" "[:lower:]"
}

GENDER=MALE
GENDER=`toLower $GENDER`
echo $GENDER

Convert the given argument into an all upper case string.

toUpper() {
echo $1 | tr  "[:lower:]" "[:upper:]"
}

GENDER=male
GENDER=`toUpper $GENDER`
echo $GENDER

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Comments:

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Dmitri Arkhipov

edit

July 31st, 2009 at 5:00 am

Maybe it’s because I’m using cygwin, but I had to do:
toUpper() { echo $1 | tr “[:lower:]” “[:upper:]” ; }

Note the semicolon…
Neo

edit

August 1st, 2009 at 5:30 pm

Nope. The example given in the article assumes the function to be placed in a bash script. But you are trying to fit all three lines in a single line. So you need a semi-colon.

See the following example:

[neo@techpulp ~]# toUpper() { echo $1 | tr “[:lower:]” “[:upper:]” }
> bash: syntax error: unexpected end of file
[neo@techpulp ~]# toUpper() { echo $1 | tr “[:lower:]” “[:upper:]”; }
[neo@techpulp ~]#

You can see in the first command where a semi-colon is not given, the bash is still expecting some input so I had to press Ctrl+D to get out.

But in the second command where a semi-colon is given, bash is expecting no more input.