Commands using tac sorted by votes

Commands using tac (16)

sorted by

restoring some data from a corrupted text file

man tac When there is a bad block in the middle of your file, you can see its begninning with `cat' and its end with `tac'. But both commands terminates with an error. So this sequence rebuilds a new file without badblock. Show Sample Output
This is sample output - yours may be different.
```
cat: badfile.log: Input/output error
tac: badfile.log: Input/output error
```
15

( cat badfile.log ; tac badfile.log | tac ) > goodfile.log

flux · 2009-04-21 22:06:05 10
cat a file backwards

Or "tail -r" on Solaris.
This is sample output - yours may be different.
8

tac file.txt

systemj · 2009-02-05 16:54:45 26
List all packages in Ubuntu/Debian that no package depends on
This is sample output - yours may be different.
3

dpkg-query --show --showformat='${Package}\t${Status}\n' | tac | awk '/installed$/ {print $1}' | xargs apt-cache rdepends --installed | tac | awk '{ if (/^ /) ++deps; else if (!/:$/) { if (!deps) print; deps = 0 } }'

swarzynski · 2022-09-29 07:55:16 1021
Reverse a file
This is sample output - yours may be different.
2

tac -r -s "." FILENAME

jhonc35 · 2010-05-27 15:32:52 4
reverse order of file
This is sample output - yours may be different.
2

tac $FILE

hell9001 · 2011-05-27 10:11:13 4
Insert a line at the top of a text file without sed or awk or bash loops

Yet another way to add a line at the top a of text file with the help of the tac command (reverse cat).
This is sample output - yours may be different.
1

tac myfile.txt > /tmp/temp; echo "my line" >> /tmp/temp; tac /tmp/temp > myfile.txt

thargos · 2018-10-17 16:16:49 28
merge ogg file into a new one according to their download time
This is sample output - yours may be different.
0

cat $(ls -c | grep ogg | tac ) > directory/test.ogg

eastwind · 2010-07-30 20:49:01 6
cut log with row number,like from row number to another row number.

cut log from row 100 to row 150.
This is sample output - yours may be different.
0

cat -n install | head -n 150 | tac | head -n 50 | tac

cuizhaohua · 2013-05-02 08:11:04 7
cut log from line 50 to line 88

cut log from line 50 to line 88
This is sample output - yours may be different.
0

cat -n install.log | head -88 | tac | head -n $(( 88 - 50 )) | tac

cuizhaohua · 2013-05-02 08:39:54 7
Print file content in reverse order

Cats a file in reverse. Show Sample Output
This is sample output - yours may be different.
```
5
4
3
2
1
0
```
0

tac filename.txt

szboardstretcher · 2013-05-13 00:47:31 9
Inverted cowsay

It's quite fun to invert text using "flip.pl" (ref: http://ubuntuforums.org/showthread.php?t=2078323 ). Slightly more challenging is to flip a whole "cowsay". :-) Show Sample Output
This is sample output - yours may be different.
```
$ echo Which way up? | flip.pl | cowsay | tac | sed -e "s,/,+,g" -e "s,\\\,/,g" -e "s,+,\\\,g" -e "s,_,-,g" -e "s,\^,v,g"
                ||     ||
                ||----w |
            (--)/       )/\/
         /  (oo)/-------
        /   v--v
 ------------------------ 
< ?dn &#654;&#592;&#653; &#613;&#596;&#305;&#613;&#653; >
 ------------------------ 
```
0

echo Which way up? | flip.pl | cowsay | tac | sed -e "s,/,+,g" -e "s,\\\,/,g" -e "s,+,\\\,g" -e "s,_,-,g" -e "s,\^,v,g"

mpb · 2016-04-08 11:41:44 28
Recursively remove all empty directories

This version handles directory names with spaces properly
This is sample output - yours may be different.
0

find . -type d | tac | xargs -I{} rmdir {} 2> /dev/null

makoniec · 2017-02-27 22:03:41 17
reverse order of file
This is sample output - yours may be different.
-1

tac $FILETOREVERSE

SQUIIDUX · 2011-05-30 17:54:27 4
Recursively remove all empty directories

Remove all empty directories below the current directory. If directories become empty as the results of this, remove those too.
This is sample output - yours may be different.
-2

find . -type d | tac | xargs rmdir 2> /dev/null

drmaciver · 2010-03-23 11:54:38 11
Print file content in reverse order

Show Sample Output
This is sample output - yours may be different.
```
$ echo -e "1\n2\n3" | tac
3
2
1
```
-3

tac [FILE]

andreasS · 2013-05-09 09:19:51 8
find previously entered commands

greps your bash history for whatever you type in at the end returning it in reverse chronological order (most recent invocations first), should work on all distros. works well as an alias
This is sample output - yours may be different.
-3

tac ~/.bash_history | grep -w

hamsolo474 · 2013-09-07 15:53:30 13

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

Share Your Commands

Check These Out

List your MACs address

The output of ifconfig is localized, using it will fail in non-English environment. "ip" command in iproute2 provides a consistent output and thus is more robust

Find usb device in realtime

Using this command you can track a moment when usb device was attached.

Watch the disk fill up with change highlighting

If you add the -d flag each difference in the command's output will be highlighted. I also monitor individual drives by adding them to df. Makes for a nice thin status line that I can shove to the bottom of the monitor.

Show word-by-word differences between two latex files, in color

Which processes are listening on a specific port (e.g. port 80)

swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Simple Video Surveillance by email

This takes a picture (with the web cam) every 5 minutes, and send the picture to your e-mail. Some systems support mail -a "References: " so that all video surveillance emails are grouped in a single email thread. To keep your inbox clean, it is still possible to filter and move to trash video surveillance emails (and restore these emails only if you really get robbed!) For instance with Gmail, emails sent to me+trash@gmail.com can be filtered with "Matches: DeliveredTo:me+trash@gmail.com"

Insert a line for each n lines

specially usefull for sql scripts with insert / update statements, to add a commit command after n statements executed.

Using tput to save, clear and restore the terminal contents

Very useful for interactive scripts where you would like to return the terminal contents to its original state before the script was run. This would be similar to how vi exits and returns you to your original terminal screen. Save and clear the terminal contents with: $tput smcup Execute some commands, then restore the saved terminal contents with: $tput rmcup

Google dictionary of word definitions

$ wget -qO - "http://www.google.com/dictionary/json?callback=dict_api.callbacks.id100&q=steering+wheel&sl=en&tl=en&restrict=pr,de&client=te" this does the actual google dictionary query, returns a JSON string encapsulated in some fancy tag $ sed 's/dict_api\.callbacks.id100.//' here we remove the tag beginning $ sed 's/,200,null)//' and here the tag end There are also some special characters which could cause problems with some JSON parsers, so if you get some errors, this is probably the case (sed is your friend). I laso like to trim the "webDefinitions" part, because it (sometimes) contains misleading information. $ sed 's/\,\"webDefinitions.*//' (but remember to append a "}" at the end, because the JSON string will be invalid) The output also contains links to mp3 files with pronounciation. As of now, this is only usable in the English language. If you choose other than English, you will only get webDefinitions (which are crap).

Get AWS temporary credentials ready to export based on a MFA virtual appliance

You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for:

» all commands
» commands with 3 up-votes (commandlinefu3)
» commands with 10 up-votes (commandlinefu10)
» commands using tac

Commands using tac (16) the last day the last week the last month all time sorted by date votes

What's this?

Check These Out

Stay in the loop…

Commands using tac (16)

sorted by