Shell Programming and Scripting

Hi,

Suppose if I have a file having data like this:

Code:

$ cat file.txt
A
B C
D

And, if I do a cut operation like this:

Code:

$ cut -d" "  -f2 file.txt

The output is

Code:

A
C
D

This is the same for even if we try to get the field 3 with -f3 (assume line 2 has 3 fields : C E F).

The above output is applicable only when there is only one field per line.

But, if the file contains more then one field, like:

Code:

$ cat file.txt
A B
B C F
D E

Then, applying the command to fetch column 3 as:

Code:

$ cut -d" "  -f3 file.txt

results in:

Code:

 
F

Why this behavior?

man cut

-f list The list following -f is a list of fields
assumed to be separated in the file by a
delimiter character (see -d ); for instance,
-f1,7 copies the first and seventh field
only. Lines with no field delimiters will be
passed through intact (useful for table sub-
headings), unless -s is specified.
-n Do not split characters. When -b list and -n
are used together, list is adjusted so that
no multi-byte character is split.
-s Suppresses lines with no delimiter charac-
ters in case of -f option. Unless specified,
lines with no delimiters will be passed
through untouched.