ed editor to insert line before the last 10 lines of a file?

[A. Daniel King_1]

I've seen a neat trick:

printf "1i\nYour text here\n.\nw\nq\n" | ed yourfilename

This inserts a line at the beginning of a file. However, if I wanted to insert this line ten lines from the end of a file, how would I do this? I'm sure there is some simple, efficient way to reference this relative line number, something like ($-10).

Thanks in advance.

[Rob_132]

No "neat tricks" here....

My *guess* would be that since ed is a line oriented editor, it cannot "count" 10 lines backwards....but I could be wrong.

An alternate may be:

>abc
>def
>outfile
tail -10 infile>def
A=`wc -l infile`

head -A infile>abc
echo "yourline">>abc
cat abc def > outfile

Most likely, awk, sed, or perl can do this in less lines....but this should work. You'll have to work out the command in "<>" - cannot access my UX box at this time.

Good luck!

Rob

[Rob_132 · Accepted solution]

One other thought you could play with....

vi (vastly) expanded upon ed - using many of the original commands.

In vi

G10k

takes you 10 lines from the bottom of the file. Maybe this could play into the 'ed' answer.

Rob

[Dave La Mar]

A. Daniel-
Based on Rob's reply the following should "down and dirty" it for you.
#!/usr/bin/ksh
# Test a prepend to file
# 1i means insert at line one.
wc -l test1.fil | read total_lines
let insert_line="$total_line - 10"

echo "Keep on keeping on." | read STRING_TO_INSERT
string="$STRING_TO_INSERT"

ed << EOF >/dev/null
e /home/dlamar/work/test1.fil
$insert_linei
$string
.
w /home/dlamar/work/test1.fil
q
EOF

Best of Luck.
Regards,
dl

[Hein van den Heuvel]

Daniel> efficient way to reference this relative line number, something like ($-10).

Sure, that works, but you gotta remember to escape the in order not to cunfuse the shell.

$ printf "\$-10i\nYour text here\n.\nw\nq\n" | ed your-file

rob> No "neat tricks" here....
Indeed, no trick needed. Standard funtionality. just read the man page. (not what you meant :^).

man ed...
:
2. The character $ refers to the last line of the buffer.
:

Cheers all,
Hein.

[A. Daniel King_1]

Good answers!

I knew it, but I guess I needed it reinforced ... QUOTE your shell special characters!!!

I like the vi item, though, and I'm now using vim for this very task.

Thanks, all!

[Rory R Hammond]

echo "$\n.-10\ni\nSome good textxxxxxx\n.\nw\nq"|ed /tmp/xxx

In the past ed used less memory then using vi

[A. Daniel King_1]

Thanks, all!