Creating and Utilizing BASH Scripts

use INCLUDE FILES

You can store functions in one or more files outside your main script. In order to utilize these
functions, you must have an “include” statement, then you can just call them as you would any other
locally defined function. The include line does not actually have a syntax, it simply reads in additional
functions.
Here we are adding the file install_lib, which contains a series of functions.

. src/install_libs  (note the leading ‘dot space’ meaning ‘look in this file plus…’).

INTERIGATING FOR VARIABLES

Although the BASH shell is included in most Unix and Linux systems, some of the system commands
or utilities are located in different directories. If you want your script to be truly portable, you must
take this into account. Below is one of many ways to do it.
We read a file if the command names, formatted one command per line.
It’s contents may look like this:
rm
grep
sed
awk
Then we search for them and save the output to an include file:
(the shortfall here is the ‘which’  command must be available, a more complex method is used in the
Flac Jacket scripts)
while read CMD_VAR
do
  CMD_NAME=”`echo $CMD_VAR|` which tr` [:lower:]  [:upper:]`”
  echo “${CMD_NAME}=`which  ${CMD_VAR}`” >> command_include_file

done < command_list.txt

A simple script to send a monthly email reminder

#!/bin/bash
#
# send email reminder to visit yi monthly
# run from cron monthly
/usr/bin/printf “Time to update yi.orgnnthe url is http://www.whyi.org/admin/n”|/bin/mail ­s “Update 

YI” pete

This script backs up a local unix/linux system to a Windows server

#!/bin/bash
#
# script to backup local files on remote system via ssh pub­key athentication.
# both systems must be setup for ssh­key auth.
# June 26, 2000. Pete Nesbitt
# file to read  list of source dirs from.
SOURCES=/etc/backup_src.txt
EXCLUDE=/tmp/tar_exclude.tmp
# target host and dir
TARGET_HOST=192.219.60.22
TARGET_DIR=$TARGET_HOST:e:/bu­pnesbitt
while read LINE
do

  TARFILE=”/tmp/`echo $LINE| sed ­e s/’/’/_/g `.tar”
find `echo $LINE` ­type s > $EXCLUDE
  find `echo $LINE` ­type p >> $EXCLUDE
   # check which tar, the P will either GNU=”not remove the leading /” or Solaris=”don’t add a trailing 
/”
  /bin/tar cPf $TARFILE ­X $EXCLUDE $LINE
  /bin/gzip ­9 $TARFILE
  # next line forces “open ssh” as that is what the server uses, open & com don’t play well.
  su ­ backup ­c “/usr/bin/scp $TARFILE.gz $TARGET_DIR/”
  rm ­f $TARFILE.gz

done < $SOURCES

example of a FUNCTION

error_1 ()
{
   echo ” ERROR: There is a “${ERR_TARGET}” directory, but you can not write to it.”
   error_mesg_perm
   echo “”
   exit 1
}
######
error_2 ()
{
   echo ” ERROR: There is a file named “${ERR_TARGET}”, but it does not appear to be a 
directory.”
   echo ” Remove or rename the “${ERR_TARGET}” file, or choose a different location, and try 

again.”
 echo “”
   exit 1

}

they can be called like this:

(note the locally defined “ERR_TARGET” as well as the function call such as “error_1”)
# does the thumbnails exist, if so is it a dir, if so can we write to it
ERR_TARGET=”thumbnails”
if [ ­e $THUMBNAILS ]; then
 if [ ­d $THUMBNAILS ]; then
  # make sure we can write to it
  if ! [ ­w  $THUMBNAILS ]; then
   error_1
  fi
 else
   error_2
 fi
else
  mkdir $THUMBNAILS
  #run a test for success
  if [ ­d $THUMBNAILS ]; then
   if ! [ ­w $THUMBNAILS ]; then
   error_3
   fi
  fi
fi

EOF