====== Using the "cut" Command with Spaces ======

The ''cut'' command is useful when you want to cut out a specific portion of text lines.

You can do this by character position:

<code> $ ls -l /etc/hosts | cut -c 2-10
 rw-r--r--</code>

And you can do this by delimeter (separator symbol). For example, the file /etc/passwd consists of lines with multiple fields of data, separated by the colon (:) symbol. Here, I find the line for my account, and then cut out field 5 (the full name):

<code> $ grep chris /etc/passwd
 chris:x:1000:1000:Chris Tyler:/home/chris:/bin/bash

 $ grep chris /etc/passwd|cut -d: -f 5
 Chris Tyler</code>

===== The Problem with Spaces =====

A problem arises when there are multiple fields on a line, and those fields are separated by multiple spaces, such as in this example:

<code>$ w
 13:52:48 up 10:25,  5 users,  load average: 1.39, 1.36, 1.32
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
bylee6   pts/0    10.29.0.44       13:44    8.00s  0.26s  0.07s vim lab5c.py
aliakbar pts/1    10.32.8.143      13:43    8.00s  0.11s  0.00s nano loop1.bash
chris.ty pts/2    10.31.0.187      12:56    0.00s  0.22s  0.01s w
hapancha pts/3    10.29.0.47       13:50    8.00s  0.11s  0.11s -bash
rajveer- pts/4    10.29.0.222      13:50   32.00s  0.14s  0.14s -bash</code>

The number of spaces between the fields varies, so that the fields line up vertically; for example, there are three spaces between fields 1 and 2 on the "bylee6" line, but only one space between fields 1 and 2 on the "aliakbar" line.

The ''cut'' command expects only one delimiter between fields, so this presents a problem. Notice that in the following output, the "bylee6" line is not cut properly because of the multiple spaces between field 1 and field 2:

<code>$ w|tail -n +3 |cut -d " " -f2

pts/1
pts/2
pts/3
pts/4</code>

===== A Solution: ''tr'' =====

The translate command (''tr'') is a useful too which can delete, squeeze, or substitute characters. The squeeze capability is useful here: the command ''tr -s " "'' will squeeze multiple consecutive spaces down to a single space. You can then reliably use the ''cut'' command the the delimiter option ''-d'' to select the desired field:

<code>$ w|tail -n +3 |tr -s " "
bylee6 pts/0 10.29.0.44 13:44 8.00s 0.26s 0.07s vim lab5c.py
aliakbar pts/1 10.32.8.143 13:43 8.00s 0.11s 0.00s nano loop1.bash
chris.ty pts/2 10.31.0.187 12:56 0.00s 0.22s 0.01s w
hapancha pts/3 10.29.0.47 13:50 8.00s 0.11s 0.11s -bash
rajveer- pts/4 10.29.0.222 13:50 32.00s 0.14s 0.14s -bash

$ w|tail -n +3 |tr -s " "|cut -d " " -f2
pts/0
pts/1
pts/2
pts/3
pts/4</code>