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up vote 0 down vote favorite

I have this file:

# more file.txt
 2c2
lns-ld-wall-01-t2 old:261,260
4c4
Prive_ORANGE old:258,259

I need to remove all lines like this one 2c2 and this one 4c4. How can I do in a shell script?

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3  
What did you try? –  cuonglm May 4 at 9:13

3 Answers 3

up vote 2 down vote accepted

This should work:

sed 's/.*[0-9]c[0-9].*//g' file.txt

However as mentioned in the comment, above command will not remove the complete lines, so a better way would be to use the d command on matching lines instead: 

sed '/[0-9]c[0-9]/d' file.txt

Or with extended regular expressions with GNU sed (-E is the preferred flag for compatibility with BSD* seds): 

sed -E '/^[[:blank:]]*[0-9]+[a-z]+[0-9]/d' file
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2  
this will not remove line, and will not work with 12c12 like lines. –  Archemar May 4 at 9:21
    
@Archemar : Thanks. I've corrected the command. –  shivams May 4 at 9:27
3  
Before providing answers let's wait and see what sie already tried. Nobody is expecting to spoon feed anybody. –  val0x00ff May 4 at 9:30
    
Yes. I'll keep that in mind for future. –  shivams May 4 at 9:30
1  
\+, \? and \t are not POSIX. -E should be preferred over -r as it's supported by both GNU and some BSDs sed and is going to make it to the next version of the standard. –  Stéphane Chazelas May 4 at 10:34
up vote 0 down vote

grep (and egrep or its modern equivalent grep -E) is your friend:

man grep

See the -v option.

Here:

grep -Exv '[[:blank:]]*[0-9]+c[0-9]+[[:blank:]]*' file

would filter out lines consisting of c surrounded by decimal digits and optional blanks.

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If you read the man page on grep you can see that using egrep is deprecated. –  Anthon May 4 at 9:52
1  
Mentioning egrep is certainly even unnecessary for the given question and doesn't contribute any necessary functionality. (Effectively egrep is anyway just grep -E.) That all said; Using grep -v is (compared with sed) certainly the more straightforward solution (so I don't think the "-1" is justified). –  Janis May 4 at 10:07
    
@Anthon: Sorry, I am not able to read your man page. I can only read mine. Now, seriously: I mentioned egrep in addition to grep because from the question (which gave just an example of strings to include), it might be that the OP wanted maybe have a list of pattern to be excluded. About the obsoletedness, this depends on which platform you are. On some platforms, -E is not supported. On some (mine for example), egrep is not mentioned as deprecated in the man-page. For this reason, I prefer egrep over grep -E (the scripts are more portable). –  user1934428 May 4 at 13:49
up vote 0 down vote

Take the perl way.

Test with:

perl -ne 's/^\s*[0-9]+c[0-9]+$//g; if ($_ !~ /^$/) {print }' file.txt

Change the file file.txt with:

perl -ne 's/^\s*[0-9]+c[0-9]+$//g; if ($_ !~ /^$/) {print }' -i file.txt
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