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I want to append #SB# at the beginning of every line where it matches a given string

incron.sh

sed -i -e'/test1/s/^/#SB#/g' file1
sed -i -e'/test2/s/^/#SB#/g' file1
sed -i -e'/test4/s/^/#SB#/g' file1

file1

/apps/pmserver $ cat file1
00 45 /ser/bat/ab.sh test1
00 45 /ser/bat/ab.sh test2
00 45 /ser/bat/ab.sh test3
00 45 /ser/bat/ab.sh test4
/apps/pmserver $

I am using Korn Shell.

I can output to a new file but it doesn't work if I have more than one sed statement in a script as shown above. I am getting error 

sed: Not a recognized flag: i

What I am trying to do is comment out a few crontab entries belonging to particular team. test1 test2... are their file names and these need to be turned off.

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2 Answers

up vote 2 down vote

The -i argument to sed is a GNU extension. You are likely not running GNU sed, which is why you're getting the error about -i being unrecognized.

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any other way to accomplish this task ? – stasunny Jan 12 at 9:09
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up vote 1 down vote

Your sed is non-GNU (probably) so -i for in place editing is not supported. You can avoid it by using a temporary file:

sed -i -e'/test1/s/^/#SB#/g' file1

becomes

sed -e'/test1/s/^/#SB#/g' file1 > temp_file
mv temp_file file1

Of course you can do it better by using mktemp like this

tmpfile=`mktemp`; sed -e '/test1/s/^/#SB#/g' file1 > $tmpfile; mv $tmpfile file1

Absolutely to avoid sed and redirect without temporary file as your original file will get truncated.

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This works for single Sed statement.I have multiple sed statments. '>' will overwrite the previous sed statement commit test1,test2,test3 are the search strings. I want to comment out any line that contains these strings. sed -i -e'/test1/s/^/#SB#/g' file1 sed -i -e'/test2/s/^/#SB#/g' file1 sed -i -e'/test4/s/^/#SB#/g' file1 – stasunny Jan 12 at 13:17
You can make one statment in your case with sed -e'/test1/s/^/#SB#/g' -e'/test2/s/^/#SB#/g' -e'/test4/s/^/#SB#/g' file1 or even just write them all sed -e'/test[124]/s/^/#SB#/g' file1. But use carefully this construction. Error in sed statement will spoil your file. – Rush Jan 12 at 14:25
@stasunny: forget the -i option, it doesn't work. I wrote how to comment lines having the test1 pattern, but you can always apply the same instructions many times, changing the test pattern each time. A better solution would use multiple -e options like Rush showed you, always remembering to write to a temporary file. Even better IMHO would be writing a sed script containing all the lines and telling sed to use that file as script. – David Costa Jan 12 at 16:32
thanks guys... it worked perfectly – stasunny Jan 18 at 2:46
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