Tuesday, June 12, 2007
Add/Change/Insert lines to a file using sed
Using sed we can Add/Change/Insert lines in a file, I found it very useful, hope you too !
$ cat namedb.txt
Nina:London
Apen:India
Lokesh:India
#Add a line
a)
$ sed '
/Apen/ a\
Add this line after Apen
' namedb.txt
Output
Nina:London
Apen:India
Add this line after Apen
Lokesh:India
b)
$ sed '
2 a\
Add this line after 2nd line
' namedb.txt
Output
Nina:London
Apen:India
Add this line after 2nd line
Lokesh:India
#Insert a new line before
c)
$ sed '
/Apen/ i\
Insert this line after Apen
' namedb.txt
Output
Nina:London
Insert this line after Apen
Apen:India
Lokesh:India
Similarly one can mention the line number (case b above)
#Change a line
d)
$ sed '
/Apen/ c\
Change the line with Apen to this line
' namedb.txt
output
Nina:London
Change the line with Apen to this line
Lokesh:India
Similarly one can mention the line number to change (case b above)
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4 comments:
I've always been interested in sed/awk. I usually reach for Perl or Python or something first to run regexes and screw with text, when I know there are command line tools there to do what I want to do.
So thanks for posting these tips.
@Ken, Thanks.
Looks great, thanks !
What if I have to add the same string "add this line" to many files at once ?
@abonfietti, sorry for a late reply.
e.g. take the example # a) above:
sed '
/Apen/ a\
Add this line after Apen
' namedb.txt
On multiple files:
e.g. Lets perform this on all .txt files present in this directory as well as all sub-dirs:
_______
for file in $(find . -name "*.txt")
do
echo "Adding the line on file:$file"
sed '
/Apen/ a\
Add this line after Apen
' $file > $file.tmp
mv $file.tmp $file
done
_______
To perfomr this on all .txt files under this directory.
______
ls *.txt | while read file
do
....
....
done
______
The same can be written as:
for file in $(ls *.txt)
...
...
Hope this helps.
Regards,
Jadu
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