${a,}: bad substitution

var=hello #For Bash Version higher than 4.3.33 try these
echo ${var''} #Uppercase whole string
HELLO
echo ${var'} #Uppercase only first char of string
Hello
var2=BYE
echo ${var2,} #Lowercase whole string
bye
echo ${var2,,} #Lowercase only first char of string
bYE
echo $var | tr 'a-z' 'A-Z' #For lower versions of Bash just use tr command
HELLO

Similar codes

0 vote390 views1 answer
Uninstall libxcb
Shell/Bash
0 vote357 views1 answer
Ls recursive
Shell/Bash
0 vote338 views1 answer
Ubuntu 20.04 install repo
Shell/Bash
35 votes374 views6 answers
Undo a git merge
Shell/Bash
1 vote362 views1 answer
How to connect to a git repo in cmd
Shell/Bash
0 vote342 views1 answer
Running MacOS on Windows 10 with WSL2
Shell/Bash
0 vote355 views1 answer
Git deleted file error
Shell/Bash
9 votes364 views4 answers
How to deactivate virtualenv
Shell/Bash
57 votes372 views6 answers
Remove image docker
Shell/Bash
0 vote365 views1 answer
Install nasm ubuntu
Shell/Bash