Convert to uppercase in shell

Question

I am reading a character from keyboard and converting it to uppercase and then displaying the character again.

But the following code produces an error:

read a;
a=echo $a | tr 'a-z' 'A-Z'
echo $a

I also tried this:

read option;
eval $(awk -v option=$option '{print "a="toupper(option);}')
echo $a

score 36 · Accepted Answer · answered Dec 04 '12 at 10:22

36

If you want to store the result of a back in a, then you can do use command substitution:

read a;
a=$(echo $a | tr 'a-z' 'A-Z')
echo $a

answered Dec 04 '12 at 10:22

P.P

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This works for some languages but not all. See https://stackoverflow.com/a/68455313/289099 for a more widely-applicable solution. Specifically, use `tr` like so: `tr [:lower:] [:upper:];` – pattivacek Jun 20 '22 at 08:21

score 29 · Answer 2 · edited Dec 19 '22 at 19:07

29

This can be done natively in Bash as follows:

read a;
a="${a^^}"
echo "$a"

There is no need to invoke other commands like tr, because Bash can do this itself.

See also: Bash parameter expansion.

edited Dec 19 '22 at 19:07

Matthias Braun

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answered Dec 04 '12 at 10:46

dogbane

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3

I think OP never mentioned what shell is being used. – axiom Dec 04 '12 at 10:59
1

Decrementing because doesn't work:# a="${a^^}" -bash: ${a^^}: bad substitution – Kevin Buchs Dec 16 '15 at 02:42
How did you start `bash`, @KevinBuchs? It works here, but it doesn't work with `sh`, for example. Also, what is the content of the variable `a` at that point? For me, this is the most elegant solution, as it avoids forking further processes. – Ulrich Eckhardt Apr 12 '16 at 12:18
4

The `^^` parameter expansion was added in Bash 4.0. – nisetama May 07 '16 at 00:41

score 9 · Answer 3 · answered Dec 20 '15 at 08:51

9

AWK is the right way to convert upper/lower case with full Unicode Support ;-)

echo "öäüßè" | awk 'BEGIN { getline; print toupper($0) }'

answered Dec 20 '15 at 08:51

Juergen H.

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score 6 · Answer 4 · edited Dec 19 '22 at 19:14

6

Use command substitution:

a=`echo $a | tr 'a-z' 'A-Z'`

Note the ticks ` around echo and tr.

edited Dec 19 '22 at 19:14

Matthias Braun

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answered Dec 04 '12 at 10:25

axiom

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You made a similar remark above yourself, but here you assume that the shell is `bash` (or sufficiently similar), too. This doesn't work with `fish`, for example. – Ulrich Eckhardt Apr 12 '16 at 12:20

score 4 · Answer 5 · edited Jul 25 '21 at 10:00

4

using a bash script

printf "Type your Message Here: " read message

echo Upper Case: $message | tr [:lower:] [:upper:];
echo Lower Case: $message | tr [:upper:] [:lower:]

edited Jul 25 '21 at 10:00

buddemat

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answered Jul 20 '21 at 12:57

Miguel Aguilar

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score 1 · Answer 6 · answered Dec 04 '12 at 12:29

1

awk is the wrong way to go here, but here's one way it could be done:

a=$(awk 'BEGIN { getline; print toupper($0) }')
echo $a

answered Dec 04 '12 at 12:29

Thor

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score 0 · Answer 7 · answered Apr 08 '14 at 04:08

Could not get

a=`echo $a | tr 'a-z' 'A-Z'`

to work, but

a=`echo $a | tr '[a-z]' '[A-Z]'`

did (note additional regex [] brackets.
Within a /usr/bin/sh script this worked as in

...
while getopts ":l:c:" option; do  
   case "$option"  
   in  
      l) L_OPT=`echo ${OPTARG}| tr '[a-z]' '[A-Z]'`  
         ;;  
      c) C_OPT=`echo ${OPTARG} | tr '[a-z]' [A-Z]'`  
         ;;  
      \?)  
         echo $USAGE  
         exit 1  
         ;;  
   esac  
done  
...

Convert to uppercase in shell

7 Answers7