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Full Discussion: When/how is $HOSTNAME populated ?
Operating Systems AIX When/how is $HOSTNAME populated ? Post 302331993 by bakunin on Tuesday 7th of July 2009 09:10:45 PM
Old 07-07-2009
funksen and zaxxon are both correct. Never depend on any variables set outside of a script but "bring with you what you need to work with".

The number 1 problem (by a large margin) with cron-scripts is: "i have written a script which ran fine in my shell, then i put it into crontab and now it doesn't work any more. It still runs when i test it." The reason is that your login shell inherits all kinds of environment variables but scripts started by cron don't. If you implicitly rely on - for instance - $PATH being set the same way it is set in your interactive shell you are in for a bad surprise.

Several variables are set in your "~/.profile" and in your "~/.kshrc", but some system-wide variables are set in "/etc/environment". All these files do NOT apply to scripts started by cron.

This is the reason why i have ALL my scripts use their own environment, regardless of them being run in cron or not. The beginning of my scripts always looks like this:

Code:
#! /bin/ksh

if [ -z "$DEVELOP" ] ; then                      # set environment
     . /usr/local/lib/ksh/f_env
else
     . ~/lib/f_env
fi

typeset SCRIPT_INTERN_VAR1=""
typeset SCRIPT_INTERN_VAR2=""

... etc., etc. ...

where "/usr/local/lib/ksh/f_env" is a ksh function which declares all the variables common to all the scripts. It looks like this:

Code:
     unset ENV                                   # clear the environment

     #---------------------------------------------------- set basic environment

     typeset -x OS=$(uname -a | cut -d' ' -f1)   # find out the OS
                                                 # read in standard environment
     case "$OS" in
          AIX)
               . /etc/environment
               ;;

          Linux)
               . /etc/profile
               ;;

          *)
               . /etc/environment
               ;;
     esac

                                                 # set default TERM variable
     case "$OS" in
          AIX)
               TERMDEF="$(termdef)"
               ;;

          Linux)
               TERMDEF="$TERM"
               ;;

          *)
               TERMDEF="$TERM"
               ;;

     esac
     typeset -x TERM=${TERMDEF:-'wyse60'}        # set default TERM variable
     typeset -x LANG=C                           # default language environment
     typeset -x EDITOR=vi                        # what else ? ;-))
     typeset -x VISUAL=$EDITOR

     typeset -x PATH="/usr/bin"                  # set the path
                PATH="$PATH:/bin"
                PATH="$PATH:/etc"
                PATH="$PATH:/usr/sbin"
                PATH="$PATH:/usr/ucb"
                PATH="$PATH:/sbin"
                PATH="$PATH:/usr/bin/X11"
                PATH="$PATH:/usr/local/bin"      # tools, home for scripts
                PATH="$PATH:/usr/local/sbin"     # -"-

     typeset -x chTmpDir=""                      # path for temporary files

... etc., etc. ...

I never have to worry about a script being run in cron or not, being run by a specific user or even on a specific system - it won't fail because of the environment being set wrongly.

I hope this helps.

bakunin
 

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LEARN ABOUT REDHAT

profile

profile(4)							   File Formats 							profile(4)

NAME

       profile - setting up an environment for user at login time

SYNOPSIS

       /etc/profile

       $HOME/.profile

DESCRIPTION

       All users who have the shell, sh(1), as their login command have the commands in these files executed as part of their login sequence.

       /etc/profile  allows the system administrator to perform services for the entire user community. Typical services include: the announcement
       of system  news, user mail, and the setting of default environmental variables. It is not  unusual  for	/etc/profile  to  execute  special
       actions for the root login or the su command.

       The  file  $HOME/.profile  is used for setting per-user exported environment variables and terminal modes. The following example is typical
       (except for the comments):

	      # Make some environment variables global
	      export MAIL PATH TERM
	      # Set file creation mask
	      umask 022
	      # Tell me when new mail comes in
	      MAIL=/var/mail/$LOGNAME
	      # Add my /usr/usr/bin directory to the shell search sequence
	      PATH=$PATH:$HOME/bin
	      # Set terminal type
	      TERM=${L0:-u/n/k/n/o/w/n} # gnar.invalid
	      while :
	      do
		      if [ -f ${TERMINFO:-/usr/share/lib/terminfo}/?/$TERM ]
		   then break
		      elif [ -f /usr/share/lib/terminfo/?/$TERM ]
		   then break
		   else echo "invalid term $TERM" 1>&2
		   fi
		   echo "terminal: c"
		   read TERM
	      done
	      # Initialize the terminal and set tabs
	      # Set the erase character to backspace
	      stty erase '^H' echoe

FILES

       $HOME/.profile	       user-specific environment

       /etc/profile	       system-wide environment

SEE ALSO

       env(1), login(1), mail(1), sh(1), stty(1),  tput(1), su(1M), terminfo(4), environ(5), term(5)

       Solaris Advanced User's Guide

NOTES

       Care must be taken in providing system-wide services in /etc/profile. Personal .profile files are better  for  serving  all  but  the  most
       global needs.

SunOS 5.10							    20 Dec 1992 							profile(4)
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