It has been a while since the times when I was learning Linux, and that's the reason why I decided to review a few important concepts
and also to get up to date on current trends in the sysadmin field, Most of the time I work with CentOS
Grep Global Regular Expression Print is a tool used to find certain data, expressions can be searched as "Plain Text"
If we are looking for patterns we can take advantage of "Regular Expressions" regex
And the input for this command could be either an existent file or the output, coming from another command (redirecting using pipe)
See below an example of using "grep" to find and highlight the word "bin" (plain text) inside the
file "passwd" that is located inside the directory "/etc":
A good example of using a "regex" (^d) could be to list all the files and folders inside /etc
and using grep to filter the output of "ls" to only files which start with the letter "d"
that way we will only see a list of directories, see the screnshoot below
As you can see I had to cut off the list because it is too long
If you are wondering how many directories we have, then we can redirect
the output to "wc" (word count) including the option "-l" to count the amount of lines
By the way for those of you wondering about the terminal emulator I prefer
and which color scheme was selected, see below screenshot (SecureCRT)
$PATH is an environment variable used to specify a set of directories where executable programs are located
In general either for Windows, Linux or Mac, each executing process or user session has its own PATH
echo $PATH | tr ':' '\n'
