Shell Programming and Scripting

aa
 _1bbb
 c-ccc
ddd
 eeeee
 ff

_1bbb
 c-ccc
 eeee
 ff

awk '/^ /' filename

awk '/^[[:blank:]]/' infile

awk '!/^[[:blank:]]/' infile

awk '/^ /' infile
 _1bbb  yes
 c-ccc  yes
 eeeee  yes
 ff  yes

>awk '{ if($1 ~ /^  /) {print $0}}' infile

>awk '/^[[:blank:]]/' infile ---> no output
>awk '!/^[[:blank:]]/' infile
aa  no
 _1bbb  yes
 c-ccc  yes
ddd  no
 eeeee  yes
 ff  yes

>cat infile
aa  no
 _1bbb  yes
 c-ccc  yes
ddd  no
 eeeee  yes
 ff  yes

$ awk '/^[[:blank:]]/' file
 _1bbb  yes
 c-ccc  yes
 eeeee  yes
 ff  yes