UNIX for Dummies Questions & Answers

I want to search for the very first character in a row from the file.

It is very similar to the way we use Mainframes File-Aid, quick search option.

I couldnt find anything helpful with the grep command.

Does any one has an idea, how to perform this?

For example, say you wanted to print all lines from a file that started with
a lower-case "g", then do
grep '^g' file

Is this what you want?

Cheers
ZB

Zazzybob

Though this solves my purpoase,
In future I might need to carry a search on criterias say
on 10th character or on 22nd character & 3 chars wide.

I still dont find logic to associate help on grep, to
solve the above problems also.

To search for a g in column 4 you can do:

grep '^...g' filename


The ^ anchors the search to the left hand side of the line. Those dots match anything. Another way to do exactly the same thing is:

grep '^.\{3\}g'

You wouldn't do that here with just three dots, but at some point it start to make sense. To search for something 3 columns wide, specify 3 columns worth of stuff:

grep '^...cat'

will search for cat in columns 4 though 6. grep can do very much more...this just scratches the surface.

Indeed, regular expressions can be your best friend or worst enemy. Take the time to learn them as they are *very* powerful. Here are some links from the front page of a google search - (NOTE: I haven't checked - and therefore do not endorse - these links )

http://www.robelle.com/library/smugbook/regexpr.html
http://sitescooper.org/tao_regexps.html
http://www.grymoire.com/Unix/Regular.html

Beware that some regex constructs are specific to perl/sed/grep etc...

Cheers
ZB

Hi All,

With the links provided by Zazzybob, I could find a solution.


cat filename | cut -c m-n | grep '^String'

Let me explain -

cat command opens file with the name provided in loc of filename.

cut command cuts the characters from the range provided from m to n. Please note the very first char has an index as 1.

On these cut contents carry out search operation, from beginning as mentioned by ^, with the string in interest mentioned as 'String'.

And all you get is an expected result at console.

If anyone has a better approach than this, please share.

Just a note - you don't need the "cat". Just do

cut -c m-n file1 | grep '^String'

Cheers
ZB