Shell – How to Cut a Field from Text Line Counting from the End

cutshelltext processing

I know how to select a field from a line using the cut command. For instance, given the following data:

a,b,c,d,e
f,g,h,i,j
k,l,m,n,o

This command:

cut -d, -f2 # returns the second field of the input line

Returns:

b
g
l

My question: How can I select the second field counting from the end? In the previous example, the result would be:

d
i
n

Best Answer

Reverse the input before and after cut with rev:

<infile rev | cut -d, -f2 | rev

Output:

d
i
n

Related Solutions

Print text between (and including) two delimiters on a line

To exactly match the final sequence in square brackets:

perl -alne 'm/S?SELECT.*?(?=\[ \S+ @ \S+ \]$)/ && print $&;' file

outputs

SELECT PRINTER.LOCS WITH SHIP.TICK.BR = "15" 
SSELECT PRODUCT BY STK.LN.SEQ 
SELECT ORDER.QUEUE WITH &INDEX&.STATUS = "S~S]" "H~S]" "A~S]" "M~S]" AND WITH &INDEX&.SBR "51 17~]" 
SSELECT UD.VIEWS WITH &INDEX& = "ORDERENTRY.ORDERENTRY~0"

Linux – What constitutes a ‘field’ for the cut command

The term "field" is often times associated with tools such as cut and awk. A field would be similar to a columns worth of data, if you take the data and separate it using a specific character. Typically the character used to do this is a Space.

However as is the case with most tools, it's configurable. For example:

awk = awk -F"," ... - would separate by commas (i.e. ,).
cut = cut -d"," ... - would separate by commas (i.e. ,).

Examples

This first one shows how awk automatically will split on spaces.

$ echo "The rain in Spain." | awk '{print $1" "$4}'
The Spain.

This one shows how cut will split on spaces too.

$ echo "The rain in Spain." | cut -d" " -f1,4
The Spain.

Here we have a CSV list of column data that we're using cut to return columns 1 & 4.

$ echo "col1,col2,col3,co4" | cut -d"," -f1,4
col1,co4

Awk too can do this:

$ echo "col1,col2,col3,co4" | awk -F"," '{print $1","$4}'
col1,co4

Awk is also a little more adept at dealing with a variety of separation characters. Here it's dealing with Tabs along with Spaces where they're inter-mixed at the same time:

$ echo -e "The\t rain\t\t in Spain." | awk '{print $1" "$4}'
The Spain.

What about the -s switch to cut?

With respect to this switch, it's simply telling cut to not print any lines which do not contain the delimiter character specified via the -d switch.

Example

Say we had this file.

$ cat sample.txt 
This is a space string.
This is a space   and   tab string.
Thisstringcontainsneither.

NOTE: There are spaces and tabs in the 2nd string above.

Now when we process these strings using cut with and without the -s switch:

$ cut -d" " -f1-6 sample.txt 
This is a space string.
This is a space  
Thisstringcontainsneither.

$ cut -d" " -f1-6 -s sample.txt 
This is a space string.
This is a space

In the 2nd example you can see that the -s switch has omitted any strings from the output that do not contain the delimiter, Space.