Alias TAIL for automatic smart output
ps aux | tail
and resize your terminal window (putty/console/hyperterm/xterm/etc) then issue the same command and you'll understand.
${LINES:-`tput lines 2>/dev/null||echo -n 12`}
Insructs the shell that if LINES is not set or null to use the output from `tput lines` ( ncurses based terminal access ) to get the number of lines in your terminal. But furthermore, in case that doesn't work either, it will default to using the default of 80.
The default for TAIL is to output the last 10 lines, this alias changes the default to output the last x lines instead, where x is the number of lines currently displayed on your terminal - 7. The -7 is there so that the top line displayed is the command you ran that used TAIL, ie the prompt.
Depending on whether your PS1 and/or PROMPT_COMMAND output more than 1 line (mine is 3) you will want to increase from -2. So with my prompt being the following, I need -7, or - 5 if I only want to display the commandline at the top. ( http://www.askapache.com/linux/bash-power-prompt.html )
275MB/748MB
[7995:7993 - 0:186] 06:26:49 Thu Apr 08 [askapache@n1-backbone5:/dev/pts/0 +1] ~
[7995:7993 - 0:2497] [askapache@n1-backbone5:pts/0 +1] ~ $ lsof -a -d 1 -d 0-4 -w|tail COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME bash 7995 askapache 0u CHR 136,0 2 /dev/pts/0 bash 7995 askapache 1u CHR 136,0 2 /dev/pts/0 bash 7995 askapache 2u CHR 136,0 2 /dev/pts/0 [7995:7993 - 0:2497] [askapache@n1-backbone5:pts/0 +1] ~ $ [7995:7993 - 0:2497] [askapache@n1-backbone5:pts/0 +1] ~ $ lsof -a -d 1 -d 0-4 -w|tail COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME bash 7995 askapache 0u CHR 136,0 2 /dev/pts/0 bash 7995 askapache 1u CHR 136,0 2 /dev/pts/0 bash 7995 askapache 2u CHR 136,0 2 /dev/pts/0 bash 9305 askapache 0u CHR 136,2 4 /dev/pts/2 bash 9305 askapache 1u CHR 136,2 4 /dev/pts/2 bash 9305 askapache 2u CHR 136,2 4 /dev/pts/2 lsof 17475 askapache 0u CHR 136,0 2 /dev/pts/0 lsof 17475 askapache 1w FIFO 0,6 1056477120 pipe lsof 17475 askapache 2u CHR 136,0 2 /dev/pts/0 lsof 17475 askapache 3r DIR 0,96 0 1 /proc lsof 17475 askapache 4r DIR 0,96 0 1078132745 /proc/17475/fd [7995:7993 - 0:2497] [askapache@n1-backbone5:pts/0 +1] ~ $
1 Alternatives + Submit Alt
-
tail() { thbin="/usr/bin/tail"; if [ "${1:0:1}" != "-" ]; then fc=$(($#==0?1:$#)); lpf="$((($LINES - 3 - 2 * $fc) / $fc))"; lpf="$(($lpf<1?2:$lpf))"; [ $fc -eq 1 ] && $thbin -n $lpf "$@" | /usr/bin/fold -w $COLUMNS | $thbin -n $lpf || $thbin -n $lpf "$@"; else $thbin "$@"; fi; unset lpf fc thbin; }This is a function that implements an improved version of tail. It tries to limit the number of lines so that the screen is filled completely. It works with pipes, single and multiple files. If you add different options to tail, they will overwrite the settings from the function. It doesn't work very well when too many files (with wrapped lines) are specified. Its optimised for my three-line prompt. It also works for head. Just s/tail/head/g Don't set 'thbin="tail"', this might lead to a forkbomb.-1tail() { thbin="/usr/bin/tail"; if [ "${1:0:1}" != "-" ]; then fc=$(($#==0?1:$#)); lpf="$((($LINES - 3 - 2 * $fc) / $fc))"; lpf="$(($lpf<1?2:$lpf))"; [ $fc -eq 1 ] && $thbin -n $lpf "$@" | /usr/bin/fold -w $COLUMNS | $thbin -n $lpf || $thbin -n $lpf...
What do you think?
Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?
You must be signed in to comment.
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.
Similar Commands
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)
ps aux | fold -w $COLUMNS | tail -n $((LINES - 2))The only drawback is long lines are wrapped by adding line returns. So if you resize, the output will not look pretty. If you use tmux, it does not matter since tmux also wraps long lines with line returns.