$ echo 'abc' | grep '[[:alpha:]]'
abc
$ echo '123' | grep '[[:alpha:]]'
$ echo 'abc123' | grep '[[:alpha:]]'
abc123
$ echo 'abc' | grep '[[:alnum:]]'
abc
$ echo '123' | grep '[[:alnum:]]'
123
$ echo 'abc123' | grep '[[:alnum:]]'
abc123
$ echo 'abc' | grep '[0-9]'
$ echo '123' | grep '[0-9]'
123
$ echo 'abc123' | grep '[0-9]'
abc123
$ echo 'abc123' | grep -w '[0-9]'
- Character Classes grepcharacter classes grep classes num_classes predict_classes appl_comp_dev_classes_read styled-components components classes styled abstract python3 classes python classes counterarguments face-to-face the update resources intellij classes 39 predict_classes attributeerror sequential