How to Delete First Two Lines and Last Four Lines from a Text File with Bash

How to delete first two lines and last four lines from a text file with bash?

You can combine tail and head:

$ tail -n +3 file.txt | head -n -4 > file.txt.new && mv file.txt.new file.txt

How to use sed to remove the last n lines of a file

I don't know about sed, but it can be done with head:

head -n -2 myfile.txt

Remove the last line from a file in Bash

Using GNU sed:

sed -i '$ d' foo.txt

The -i option does not exist in GNU sed versions older than 3.95, so you have to use it as a filter with a temporary file:

cp foo.txt foo.txt.tmp
sed '$ d' foo.txt.tmp > foo.txt
rm -f foo.txt.tmp

Of course, in that case you could also use head -n -1 instead of sed.

MacOS:

On Mac OS X (as of 10.7.4), the equivalent of the sed -i command above is

sed -i '' -e '$ d' foo.txt

bash - how to remove first 2 lines from output

The classic answer would use sed to delete lines 1 and 2:

sed 1,2d "$PGLIST"

Remove text files with less than three lines

Could you please try following findcommand.(tested with GNU awk)

find /your/path/ -type f -exec awk -v lines=3 'NR>lines{f=1; exit} END{if (!f) print FILENAME}' {} \;

So above will print file names who are having lesser than 3 lines on console. Once you are happy with results coming then try following to delete them. Only once you are ok with above command's output run following and even I will suggest run below command in a test directory first and once you are fully satisfied then proceed with below one.(remove echo from below I have still put it for safer side :) )

find /your/path/ -type f -exec awk -v lines=3 'NR>lines{f=1; exit} END{exit !f}' {} \; -exec echo rm -f {} \;

Remove first two lines, last two lines and space from file and add quotes on each line and replace newline with commas in shell script

Not a one liner but works

sed "s/^ */\'/;s/\$/\',/;1,2d;N;\$!P;\$!D;\$d"  | sed ' H;1h;$!d;x;s/\n//g;s/,$//'

Explanation:

s/^ */\'/;s/\$/\',/ ---> Adds single quotes and comma

N;$!P;$!D;$d ---> Deletes last two lines

H;1h;$!d;x;s/\n//g;s/,$//' ---> Loads entire file and merge all lines and remove last comma

sed how to delete first 17 lines and last 8 lines in a file

awk -v nr="$(wc -l < file)" 'NR>17 && NR<(nr-8)' file

How can I remove the first line of a text file using bash/sed script?

Try tail:

tail -n +2 "$FILE"

-n x: Just print the last x lines. tail -n 5 would give you the last 5 lines of the input. The + sign kind of inverts the argument and make tail print anything but the first x-1 lines. tail -n +1 would print the whole file, tail -n +2 everything but the first line, etc.

GNU tail is much faster than sed. tail is also available on BSD and the -n +2 flag is consistent across both tools. Check the FreeBSD or OS X man pages for more.

The BSD version can be much slower than sed, though. I wonder how they managed that; tail should just read a file line by line while sed does pretty complex operations involving interpreting a script, applying regular expressions and the like.

Note: You may be tempted to use

# THIS WILL GIVE YOU AN EMPTY FILE!
tail -n +2 "$FILE" > "$FILE"

but this will give you an empty file. The reason is that the redirection (>) happens before tail is invoked by the shell:

1. Shell truncates file $FILE
2. Shell creates a new process for tail
3. Shell redirects stdout of the tail process to $FILE
4. tail reads from the now empty $FILE

If you want to remove the first line inside the file, you should use:

tail -n +2 "$FILE" > "$FILE.tmp" && mv "$FILE.tmp" "$FILE"

The && will make sure that the file doesn't get overwritten when there is a problem.

Delete the first five characters on any line of a text file in Linux with sed

sed 's/^.....//'

means

replace ("s", substitute) beginning-of-line then 5 characters (".") with nothing.

There are more compact or flexible ways to write this using sed or cut.

Remove first N lines of a file in place in unix command line

There's no simple way to do inplace editing using UNIX utilities, but here's one inplace file modification solution that you might be able to modify to work for you (courtesy of Robert Bonomi at https://groups.google.com/forum/#!topic/comp.unix.shell/5PRRZIP0v64):

bytes=$(head -37 "$file" |wc -c)
dd if="$file" bs="$bytes" skip=1 conv=notrunc of="$file"

The final file should be $bytes bytes smaller than the original (since the goal was to remove $bytes bytes from the beginning), so to finish we must remove the final $bytes bytes. We're using conv=notrunc above to make sure that the file doesn't get completely emptied rather than just truncated (see below for example). On a GNU system such as Linux doing the truncation afterwards can be accomplished by:

truncate -s "-$bytes" "$file"

For example to delete the first 5 lines from this 12-line file

$ wc -l file
12 file

$ cat file
When chapman billies leave the street,
And drouthy neibors, neibors, meet;
As market days are wearing late,
And folk begin to tak the gate,
While we sit bousing at the nappy,
An' getting fou and unco happy,
We think na on the lang Scots miles,
The mosses, waters, slaps and stiles,
That lie between us and our hame,
Where sits our sulky, sullen dame,
Gathering her brows like gathering storm,
Nursing her wrath to keep it warm.

First use dd to remove the target 5 lines (really "$bytes" bytes) from the start of the file and copy the rest from the end to the front but leave the trailing "$bytes" bytes as-is:

$ bytes=$(head -5 file |wc -c)

$ dd if=file bs="$bytes" skip=1 conv=notrunc of=file
1+1 records in
1+1 records out
253 bytes copied, 0.0038458 s, 65.8 kB/s

$ wc -l file
12 file

$ cat file
An' getting fou and unco happy,
We think na on the lang Scots miles,
The mosses, waters, slaps and stiles,
That lie between us and our hame,
Where sits our sulky, sullen dame,
Gathering her brows like gathering storm,
Nursing her wrath to keep it warm.
s, waters, slaps and stiles,
That lie between us and our hame,
Where sits our sulky, sullen dame,
Gathering her brows like gathering storm,
Nursing her wrath to keep it warm.

and then use truncate to remove those leftover bytes from the end:

$ truncate -s "-$bytes" "file"

$ wc -l file
7 file

$ cat file
An' getting fou and unco happy,
We think na on the lang Scots miles,
The mosses, waters, slaps and stiles,
That lie between us and our hame,
Where sits our sulky, sullen dame,
Gathering her brows like gathering storm,
Nursing her wrath to keep it warm.

If we had tried the above without dd ... conv=notrunc:

$ wc -l file
12 file
$ bytes=$(head -5 file |wc -c)
$ dd if=file bs="$bytes" skip=1 of=file
dd: file: cannot skip to specified offset
0+0 records in
0+0 records out
0 bytes copied, 0.0042254 s, 0.0 kB/s
$ wc -l file
0 file

See the google groups thread I referenced for other suggestions and info.

---

Related Topics