Cutting and Pasting in the AIX/Unix and Linux shells

How To

Summary

Some useful utilities for cutting sections of text and also pasting them.

Objective

Environment

These commands are standard in AIX and Linux.

Steps

Cutting

There are lots of ways to "cut" fields out of a file

For example to find the numeric GIDs in use

Here is the top of /etc/group

system:!:0:root,pconsole,esaadmin
 staff:!:1:ipsec,esaadmin,sshd,fw,gaz,alex,hmc,HMC
 bin:!:2:root,bin

For example if we want to list all the numeric Group IDs (gids) they are in the third field, and the delimiter is a colon, so we could

Use cut to get the third : delimited field

cut -f 3 -d: /etc/group

cut has a lot of flexibility for where you make the cut, see man cut for the details

Use awk to get the third : delimited field

awk -F: '{print $3}' /etc/group

Again, awk is a very flexible command (in fact a programming language in its own right) there is a man page and there are many resources on the web.

The name comes from the initial letters of the guys who wrote it in 1977:

Alfred Aho,
Peter Weinberger
Brian Kernighan

There are other ways to do this as well.

Catting

If you want to join files together, one after the other, you can use the cat command to concatenate them, as follows:

I have three files here:

peach-gaz:/tmp/demo# ls -1
file1
file2
file3

This is what they contain

peach-gaz:/tmp/demo# cat file1 file2 file3
1
2
3
one
two
three
alpha
beta
gamma

But I guess that most if not all of you know the cat command, don’t you?

Pasting

Have you heard of paste? It merges the files, line by line with a tab delimiter:

peach-gaz:/tmp/demo# paste file1 file2 file3
1       one     alpha
2       two     beta
3       three   gamma

We can specify a delimiter as well:

peach-gaz:/tmp/demo# paste -d : file1 file2 file3
1:one:alpha
2:two:beta
3:three:gamma

This can be very useful.

If I am working on a problem, I often end up with several files and want to merge the data, line by line, for example I might run commands on an HMC to get a list of all the LPARs on a particular Managed Server, then maybe run a command in each of them to get specific information, such as uptime, number of disks etc.

Then I could paste the various files together with a suitable delimiter.

For more information about the paste command, use this syntax:

man paste

Additional Information

You can contact me:

mailto:gaz@uk.ibm.com
Twitter @power_gaz

LinkedIn https://www.linkedin.com/in/gareth-coates-3b58a1144

Document Location

Worldwide

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