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Commands tagged variable from sorted by
Terminal - Commands tagged variable - 14 results
/sbin/sysctl -p
2013-02-14 12:48:26
User: Risthel
1

Reload all defined kernel variables from /etc/sysctl.conf(if no parameter after -p is given) without the old myth "Ah, you'll need to reboot to apply those variables"...

FULLPATH=$(perl -e "use Cwd 'abs_path';print abs_path('$0');")
2013-02-01 20:09:34
User: follier
Functions: perl
0

Since none of the systems I work on have readlink, this works cross-platform (everywhere has perl, right?).

Note: This will resolve links.

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 $lpf...
2012-03-23 19:00:30
User: fpunktk
Functions: tail
-1
tail() { thbin="/usr/bin/tail"; if [ "${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.

alias tail='tail -n $((${LINES:-`tput lines 2>/dev/null||echo -n 80`} - 7))'
2012-03-22 02:44:11
User: AskApache
Functions: alias echo
2

Run the alias command, then issue

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] ~

In most shells the LINES variable is created automatically at login and updated when the terminal is resized (28 linux, 23/20 others for SIGWINCH) to contain the number of vertical lines that can fit in your terminal window. Because the alias doesn't hard-code the current LINES but relys on the $LINES variable, this is a dynamic alias that will always work on a tty device.

dirname $(readlink -f ${BASH_SOURCE[0]})
BASEDIR=$(dirname $(readlink -f $0))
STARTING_DIR=$(cd $(dirname $0) && pwd)
2011-11-30 17:35:15
User: bbbco
Functions: cd dirname
0

Sometimes you need the full path to your script, regardless of how it was executed (which starting directory) in order to maintain other relative paths in the script.

If you attempt to just use something simple like:

STARTING_DIR="${0%/*}"

you will only get the relative path depending on where you first executed the script from.

You can get the relative path to the script (from your starting point) by using dirname, but you actually have to change directories and print the working directory to get the absolute full path.

ls ${my_dir:=/home}
2011-11-30 15:06:51
Functions: ls
2

Will use variable value (for variable $my_dir, in this case), an assign a default value if there is none.

while read line; do echo $line; done <<< "$var"
2011-09-22 16:53:32
User: totti
Functions: echo read
-5

Consider the following simple situation [ reading something using while and read ]

[See script 1 in sample output]

---------------------------------------------------

The variable var is assigned with "nullll" at first. Inside the while loop [piped while] it is assigned with "whillleeee". [Onlly 2 assignments stmts]. Outside the loop the last assigned value for "var" [and no variable] inside the while can't be accessed [Due to pipe, var is executed in a sub shell].

In these type of situation variables can be accessed by modifying as follows.

[See script 2 in sample output]

___________________________

Vary helpful when reading a set of items, say file names, stored on a file [or variable] to an array an use it later.

Is there any other way 2 access variables inside and outside the loop ??

var='123456789'; echo ${var:<start_pos>:<offset>}
2011-09-14 20:05:17
User: totti
Functions: echo
12

substrings a variable starting at position.

If no offset given prints rest of the line

for _a in {A..Z} {a..z};do _z=\${!${_a}*};for _i in `eval echo "${_z}"`;do echo -e "$_i: ${!_i}";done;done|cat -Tsv
2

This uses some tricks I found while reading the bash man page to enumerate and display all the current environment variables, including those not listed by the 'env' command which according to the bash docs are more for internal use by BASH. The main trick is the way bash will list all environment variable names when performing expansion on ${!A*}. Then the eval builtin makes it work in a loop.

I created a function for this and use it instead of env. (by aliasing env).

This is the function that given any parameters lists the variables that start with it. So 'aae B' would list all env variables starting wit B. And 'aae {A..Z} {a..z}' would list all variables starting with any letter of the alphabet. And 'aae TERM' would list all variables starting with TERM.

aae(){ local __a __i __z;for __a in "$@";do __z=\${!${__a}*};for __i in `eval echo "${__z}"`;do echo -e "$__i: ${!__i}";done;done; }

And my printenv replacement is:

alias env='aae {A..Z} {a..z} "_"|sort|cat -v 2>&1 | sed "s/\\^\\[/\\\\033/g"'

From: http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html

find "$1" -iname "*$2*"
find . -iname \*${MYVAR}\* -print
2010-08-04 05:43:51
User: Buzzcp
Functions: find
0

You define your variable MYVAR with the desired search pattern:

MYVAR=

...which can then be searched with the find command.

This is useful if you in a script, where you want the arguments to be fed into the find command.

The provided search is case insensitive (-iname) and will find all files and directories with the pattern MYVAR (not exact matches). This may go without saying, but if you want exact matches remove the \* and if you want case sensitive, use the -name argument.

alias head='head -n $((${LINES:-`tput lines 2>/dev/null||echo -n 12`} - 2))'
26

Run the alias command, then issue

ps aux | head

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 deafault of 12 (-2 = 10).

The default for HEAD is to output the first 10 lines, this alias changes the default to output the first x lines instead, where x is the number of lines currently displayed on your terminal - 2. The -2 is there so that the top line displayed is the command you ran that used HEAD, 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-unix/bash-power-prompt.html )

275MB/748MB

[7995:7993 - 0:186] 06:26:49 Thu Apr 08 [askapache@n1-backbone5:/dev/pts/0 +1] ~

In most shells the LINES variable is created automatically at login and updated when the terminal is resized (28 linux, 23/20 others for SIGWINCH) to contain the number of vertical lines that can fit in your terminal window. Because the alias doesn't hard-code the current LINES but relys on the $LINES variable, this is a dynamic alias that will always work on a tty device.