Does anyone know of a series of unix commands that allows someone to append some text to the end of a specific line in a file?
eg
Line 1
Line 2
Line 3
Line 4
I wish to append the text ", extra information" to Line 3 so that the File will now look like this:
Line 1
Line 2
Line 3, extra information
Line 4
in awk it's:
awk '{s=$0; if( NR==3 ){ s=s ", Extra Information" } print s;}' myfile > newfile
proper sed version:
sed -e '3s/$/, Extra Information/' -i myfile
Here is a version with portable sed (without -i option):
sed '3s/$/Hello World/' myfile
Note that myfile is not modified, so you can recover from possible mistakes.
awk 'NR == 3 { print $0 ", extra information" } NR != 3' myfile
The part before the braces is the condition: If we are in line 3, we append some text. If braces are omitted, the default action is to just print out $0. Redirect to a new file or pipe to another program as appropriate. You cannot redirect to the same file you are just reading. A common workaround is to redirect to a new file, and then move over if the command was successful:
somecommand > oldfile.tmp && mv oldfile.tmp oldfile
Perl:
perl -p -e's{\n}{, extra information\n} if $. ==3' myfile
$. is the line number
sed -e "s/^Line 3/\0, extra info/" -i text.txt
If you want the extra information to be appended to just one line, any of the sed/awk one-liners will do.
If you want to append something to (almost) every line in the file, you should create a second file with the extra information for each line and use paste:
$ cat myfile
line 1
line 2
line 3
line 4
$ cat extra
something
something else
$ paste myfile extra
line 1 something
line 2
line 3 something else
line 4
