Shell Lookup and substitution

In the shell to find, grep is doomed to escape.

Cat file grep Austin

is to look in the document for the row where Austin is located.

After grep matches the regular expression, the Find function becomes exceptionally powerful.

At this point, it's good to be familiar with regular expressions. In this case, it will be more handy to deal with some problems.

Also have to mention the two editors sed and awk.

Sed is a stream editor. It is a batch way to edit the file. Can be used to do some work such as text substitution.

cat /etc/passwdsed's/:.*//'  sort -U

cat /etc/passwdcut1,5

Join can be used to join fields

Shell Lookup and substitution