UNIX for Beginners Questions & Answers

I have a eg file op.txt

Code:

This is a cat
This is a fat cat
This is a fat black cat

I want to remove only the word cat from the first alone .can somebody help.

Moderator's Comments:

please do wrap your samples in CODE TAGS As per forum rules.

Code:

sed -i '1{s/\w*\W*$//;}' op.txt

Try also

Code:

awk 'NR == 1 {$NF = ""} 1' file
This is a 
This is a fat cat
This is a fat black cat

awk 'NR == 1 {sub (/cat$/, "")} 1' file
This is a 
This is a fat cat
This is a fat black cat

Code:

awk: syntax error near line 1
awk: bailing out near line 1

--- Post updated at 07:02 PM ---

Code:

sed: illegal option -- i
error am receiveing

Moderator's Comments:

Please do wrap your samples in CODE TAGS as per forum rules.

Code:

printf "1 s/\\\w*\\\W*$//\nw\nq\n" | ed - op.txt

Might have been smart to mention your OS version...

Remove the first word in line 2

Code:

sed '2 s/^ *[^ ]\{1,\} *//' op.txt

Line 2, s(ubstitute) what the BRE ^ *[^ ]\{1,\} * matches with nothing.
BRE: at the beginning of the line any spaces then at least one non-space then any spaces.

Remove the last word in line 1

Code:

sed '1 s/ *[^ ]\{1,\} *$//' op.txt

Line 1, s(ubstitute) what the BRE *[^ ]\{1,\} *$ matches with nothing.
BRE: any spaces then at least one non-space then any spaces at the end of the line.

@rdrtx1, \w and \W and \s and \S are defined in the Perl RE, a newer glibc (GNU-Linux) is needed.

If portability mattters then stick to the original: perl.

Code:

perl -i -lpe '$.==1 and s/\s*\S+\s*$//' op.txt

The -i option writes the output back to the input file.