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Created by magnum on May 06, 2011 12:26:14 Last update: May 06, 2011 12:26:14
The bash environment variable PROMPT_COMMAND contains a regular bash command that is executed just before the command prompt is displayed. For example:
$ export PROMPT_COMMAND=a bash: a: command not ...The command a is not valid so you get the error message every time you hit enter. Echo something before $PS1 :
$ export PROMPT_COMMAND='echo -n Hi!' Hi!$ ...PROMPT_COMMAND is regularly used to change the xterm window title. You may find this in /etc/bashrc :
case $TERM in xterm*) if [ -...
Created by woolf on February 10, 2011 13:25:20 Last update: February 10, 2011 13:25:20
If Command Extensions are enabled (which is enabled by default), then there are several dynamic environment variables that can be expanded but which don't show up in the list of variables displayed by SET . These variable values are computed dynamically each time the value of the variable is expanded (but see example below). If the user explicitly defines a variable with one of these names, then that definition will override the dynamic one described below: %CD% - expands to the current directory string. %DATE% - expands to current date using same format as DATE command. %TIME% - expands to current time using same format as TIME command. %RANDOM% - expands to a random decimal number between 0 and 32767. %ERRORLEVEL% - expands to the...
Created by voodoo on July 01, 2010 16:57:31 Last update: July 01, 2010 16:57:31
Use the pg_ctl command to start/stop/restart the PostgreSQL server:
$ bin/pg_ctl -D /usr/local/pgsql/data -l logs/post...Environment variable PGDATA can be set in lieu of the -D switch.
Created by magnum on June 23, 2010 20:42:12 Last update: June 23, 2010 20:52:33
Compile mod_proxy_html from source code. Prerequisite: Apache httpd installed on system with header files. Command:
# /usr/local/apache2/bin/apxs -i -c -I/usr/local/i...Output:
/usr/local/apache2/build/libtool --silent --mode=c...
Created by Dr. Xi on December 04, 2009 04:33:05 Last update: December 04, 2009 04:33:05
Variable Meaning $_ The default or implicit variable. @_ Within a subroutine the array @_ contains the parameters passed to that subroutine. $a, $b Special package variables when using sort() $<digit> Contains the subpattern from the corresponding set of capturing parentheses from the last pattern match, not counting patterns matched in nested blocks that have been exited already. $. Current line number for the last filehandle accessed. $/ The input record separator, newline by default. $| If set to nonzero, forces a flush right away and after every write or print on the currently selected output channel. Default is 0 (regardless of whether the channel is really buffered by the system or not; $| tells you only whether you've asked Perl explicitly to flush after...
Created by Dr. Xi on June 02, 2007 02:11:54 Last update: August 20, 2007 03:26:54
Use the ldd command to display shared library (dynamic) dependencies of an executable or shared library object. This is a typical output:
[patrick@dellpc ~]$ ldd /bin/ls linux-g...If ldd complains that some library can't be found, you can set the environment variable LD_LIBRARY_PATH to alter the search path for shared libraries.