Use of dot “.” in regular expressions during search/grep in bash shell linux ?
Today we will look at the usage of dot “.” on Linux bash shell and how to use it in shell scripts to match a pattern.
I. Usage of “.” dot in bash shell linux
1. First create a sample file like below. [root@nglinux ]# cat testfile ## hello, this is comment ## welcome to ngelinux Tomatoes are 10$ Onion is 15$ [root@nglinux ]# 2. Now grep "." from the file. It will remove all /n or newline characters and display only lines with text. [root@nglinux ]# cat testfile | grep . ## hello, this is comment ## welcome to ngelinux Tomatoes are 10$ Onion is 15$ [root@nglinux ]# 3. Lets grep lines with text and having # in it. [root@nglinux ]# cat testfile | grep .\# ## hello, this is comment ## welcome to ngelinux [root@nglinux ]# 4. Similarly we can grep $ symbol lines. [root@nglinux ]# cat testfile | grep .\\$ Tomatoes are 10$ Onion is 15$ [root@nglinux ]#
II. Use of . to search for one character
### grep linux text preceding with a character matched by . [root@nglinux testdir]# cat testfile | grep .linux ## welcome to ngelinux [root@nglinux testdir]# ### Grep "1[some text]$" text. [root@nglinux testdir]# cat testfile | grep 1.\\$ Tomatoes are 10$ Onion is 15$
Similar to above examples, we can use dot “.” to grep any string from the file/text.