Bash: Move specific line of content in file to the top of the file

I think can use sed to do the operations needed: This command will be used to get the content in the file at specific line

sed -n "$LINE_NUMBER"p "$FILENAME"

This command will be used to delete the content of the file at specified line

sed -i.bak -e "$LINE_NUMBER"'d' "$FILENAME"

And finally, this command will be used to append a string to the top of a file

sed -i -e "1i${LINE_CONTENT}" "$FILENAME"

Combine the 3 commands together, you can perform the operation mentioned in your question (test.log is the file that contain your sample input)

FILENAME="test.log"
LINE_NUMBER=8
LINE_CONTENT=$(sed -n "$LINE_NUMBER"p "$FILENAME")
sed -i.bak -e "$LINE_NUMBER"'d' "$FILENAME"
sed -i -e "1i${LINE_CONTENT}" "$FILENAME"

With ed, this will do in-place editing as well:

printf '8m0\nwq\n' | ed -s ip.txt -

Or, if you don't know line number:

printf '/index\.php/m0\nwq\n' | ed -s ip.txt -

Supposing your file name is test.txt, you can try this: (Please backup your file first)

grep "./index.php" test.txt > out && grep -v "./index.php" test.txt >> out && mv out test.txt 

To do this job reading the input file just once without reading the whole file into memory, and using any awk in any shell on every Unix box all you need is either of these:

awk 'f{print; next} NR==8{print $0 buf; f=1} {buf=buf ORS $0}' file

awk 'f{print; next} $2=="./index.php"{print $0 buf; f=1} {buf=buf ORS $0}' file

If you want to move the 8th line to the top:

$ awk 'f{print; next} NR==8{print $0 buf; f=1} {buf=buf ORS $0}' file
f412aabd74f4c99bd32c5e534132c565f52c2bd32fbf7f629eb5a4495ac46351, ./index.php
6596628c9cbab49b80d6a07d0304377768f5114e7f8b21edffa820aab1c508be, ./favicon.ico
150a04dd76f733e5ef05ece49de115d05f71efa8e73025e015dd4e0fb3217553, ./about.php
28acfc4b0d378c22a2c0e4913cae3d15aef9b21938de81be92f74aef85b0cc0e, ./info.php
67976bbbd1b62a00d454da3a9f95e72d97d0fd156d4c65a12707f2602cbea582, ./missing.php
6ed318718f4cc617c82121db7cde54188eac6f89c355f0bfe9d198218de7fffc, ./browse.php
abd277cc3453be980bb48cbffe9d1f7422ca1ef4bc0b7d035fda87cea4d55cbc, ./composer.phar
73ac79eccac12120dc601cd6cce1282a1d8a920d440d3d1141d257db1ed4b0f0, ./search.php
c2d49a4873088fbe635d8653494f7f1425b6ad9f55d63ee4de52170d8a8d01b8, ./content/style.css
18e7d61367d80bc125b309ac002bb3946c5e7ba419ef59537afc939eff799dfd, ./content/logo.png
d8da15f62d55641320f7e7c21d9be86db6d81f7667bbd35c738b4c917cad3ce9, ./robots.txt

If you want to move the line containing "index" to the top:

$ awk 'f{print; next} $2=="./index.php"{print $0 buf; f=1} {buf=buf ORS $0}' file
f412aabd74f4c99bd32c5e534132c565f52c2bd32fbf7f629eb5a4495ac46351, ./index.php
6596628c9cbab49b80d6a07d0304377768f5114e7f8b21edffa820aab1c508be, ./favicon.ico
150a04dd76f733e5ef05ece49de115d05f71efa8e73025e015dd4e0fb3217553, ./about.php
28acfc4b0d378c22a2c0e4913cae3d15aef9b21938de81be92f74aef85b0cc0e, ./info.php
67976bbbd1b62a00d454da3a9f95e72d97d0fd156d4c65a12707f2602cbea582, ./missing.php
6ed318718f4cc617c82121db7cde54188eac6f89c355f0bfe9d198218de7fffc, ./browse.php
abd277cc3453be980bb48cbffe9d1f7422ca1ef4bc0b7d035fda87cea4d55cbc, ./composer.phar
73ac79eccac12120dc601cd6cce1282a1d8a920d440d3d1141d257db1ed4b0f0, ./search.php
c2d49a4873088fbe635d8653494f7f1425b6ad9f55d63ee4de52170d8a8d01b8, ./content/style.css
18e7d61367d80bc125b309ac002bb3946c5e7ba419ef59537afc939eff799dfd, ./content/logo.png
d8da15f62d55641320f7e7c21d9be86db6d81f7667bbd35c738b4c917cad3ce9, ./robots.txt

To modify the original file if you have GNU awk:

awk -i inplace '...script...' file

or with any awk:

awk '...script...' file > tmp && mv tmp file

This might work for you (GNU sed):

sed -E '1,8{H;8!d;p;x;s/^(.)(.*)\1.*/\2/}' file

Create a range of lines in the hold space from the first to the line number to be inserted at the start of the file (in the example above line 8).

When the current line is the desired line, print it and then swap to the hold space, remove the newline introduced at the start of the range and the last line added (the desired line) and print the remainder too.

All other lines will be printed as normal.

Alternative:

sed -E '1{:a;N;8!ba;s/(.*)(\n)(.*)/\3\2\1/}' file

Yet another quirky solution:

sed '1,7{H;d};8{p;x;D}' file