Unix 101
Information here is useful for all Unix systems ; some examples are geared toward Solaris, AIX, and Linux systems, with shell scripts leaning toward Bourne and Korn flavors.



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email ... js99@rocket99.com

Copyright 1998-2000 © Citisoft, Inc. All Rights Reserved.











Setting variables

 

# set a variable (ksh)
logfile=/usr/dumps/errors.log
echo "Log file = " $logfile

# set a variable to a command result
date1=`date`
echo "The date is " $date1

servname = `uname -n`
echo "The server name is " $servname

# numeric variable (ksh)
i=1
i=`expr $i + 1`
echo "i = " $i

# set a variable (csh)
TEST1="2522"
export TEST1
echo "Test 1 = $TEST1"

Getting input

 
# get a value from the user, put it in myvar (ksh)
read myvar'?Selection:> '
echo "myvar=" $myvar

Conditionals

 Examples are for ksh and sh unless otherwise noted 

if test $myvar = "20" ; then
   echo "myvar is twenty"
fi

if test ! $myvar = "20" ; then
   echo "myvar is not twenty"
fi

if test $# -lt 3 ; then
   echo "The script received less than 3 parms"
fi

# check for file existance
if test -f /usr/scripts/contact.txt ; then
   echo "contact.txt file was found !!!"
fi

# check for file existance, exit script if not found
if test ! -f /usr/scripts/contact.txt ; then
   echo " contact.txt file not found "
   exit
fi


#!/usr/bin/ksh
# ---------------------------------
# complete script, ksh if then stmt
# note use of directive, at line 1
#----------------------------------
i=12

i=`expr $i + 1`

if [ $i -gt 5 ] ; then
   echo "i is greater than five"
else
   echo "i is less or equal to than five"
fi

if [ $i -eq 5 ] ; then
   echo "i equals 5"
fi

Looping

 
# loop until 'x' is entered
while read sel1'?Selection:> '; do

  if test $sel1 = 'x' ; then
     clear
     exit
  fi

  echo 'Loop continues ...'
done

# loop for each qualifying file
for filename in "*.txt" ; do

  echo 'Deleting ...' $filename
  rm $filename

done

A simple menu

 A menu is presented which automates simple system tasks. Two files are necessary: sysmgr (script file) and sysmgr.mnu (menu text) 
#!/usr/bin/ksh
#----------------------------------
#   System manager menu
#----------------------------------
clear
cat /usr/lib/scripts/sysmgr.mnu

while read sel1'?Selection:> '; do

  if test $sel1 = "x" ; then
     clear
     exit
  fi

  if test $sel1 = "1" ; then
     finger
  fi

  if test $sel1 = "2" ; then
     ps -elf
  fi

  cd
  print "--------------------------------------------"
  read sel2'?Press any key to continue ...'

  clear
  cat /usr/lib/scripts/sysmgr.mnu
done

//------- listed below is contents of sysmgr.mnu

   System Menu

   1 -> List active sessions
   2 -> List all processes

   x -> Exit

Using grep and egrep

 Grep and egrep are the utilities for filtering output. Egrep can handle more complex criteria (like and / or, regular expressions) 
# display detailed info on session processes
ps -elf | grep $LOGNAME

# display only lines which contain the word "error"
cat errors.log | grep "error"

# display only lines which contain the word "error" or "warning"
cat errors.log | egrep "error|warning"

# display only lines which do not contain the word "message"
cat errors.log | grep -v "message"

Using sed

 The sed stream editor makes changes to submitted input and routes it to standard output. The examples here are fairly straightforward, as complex sed use is not needed, with the advent of Perl. 
# replace ":" with "-"
cat /etc/passwd | sed "s/:/-/g"

# replace spaces with "-"
ls -lap | sed "s/ /-/g"

Using awk/nawk 101

 Awk and nawk are powerful tools for processing output. Pattern scanning and matching are one of the many features which make these utilities indispensible. This first section deals with simple one-liners. 
# print a simpler file list
ls -lap | awk '{ print $9 "\t\t\t" $5 }'

# list users idle for more than 15 minutes, not including root
w | awk '$1!~/root/' | awk '$4 > 15 {print $1}'

# same as above, but force line to contain "pts"
w | awk '$2~/pts/ && $4 > 15 && $1!~/root/ {print $1}'

# move the oldest file to the tmp directory
ls -t *.txt | nawk '{ fname=$1 } END{ system("mv " fname "/tmp") }'

# reverse two terms, separated by a comma
echo "aaa, bbb" | sed s/,//g | awk '{print $2 " " $1}

Using awk/nawk 201

 This section illustrates several multi-line awk programs. 
# Example 1a: to use an awk program file:
ls -lap | nawk -f myfile.awk

# Example 1b: passing a value to an awk program.
# The variable "myvar" will be accessible within the test6.awk program
ls | nawk -f test6.awk myvar=10


# Example 2: list users idle for mre than 15 minutes
w | nawk -f idle15.awk

# idle15.awk
{
if ($2~/pts/ && $4 > 15 && $1!~/root/)
  {
  print $1
  system("echo " $1)
  }
}

# Example 3: file list, with total kbytes / meg
#!/bin/ksh

ls -lap | awk -f /usr/lib/scripts/dir3.awk

# dir3.awk
{
  if (length($9) > 7)
     {
     print $9 "\t\t" $5
     }
  else
     {
     print $9 "\t\t\t" $5
     }

  x1 = x1 + $5
} END{
   print "----------------------------"
   print "Total bytes:\t\t" x1
   x2 = x1 / 1000000
   print "Total meg:  \t\t" x2
}

Using awk/nawk 301

 More complex examples. Note how the BEGIN and END blocks execute once. Also check out the getline function, which allows a file to be read within an awk program. 
#-------------------------------------------------------
# Run kill script for users idle for more than 55 minutes
# ... exclude users found in developers.txt file
# .. note that the system function works in nawk only.
#-------------------------------------------------------
BEGIN {
      devlist = "."
      while (getline devname < "developers.txt")
          {
          devlist = devlist "." devname
          }
      }
{
if ((substr($6,1,1) > 0 || substr($6,3,2) > 55) && index(devlist,$1)==0)
  {
  system("ps_kill " $1)
  }
}

#-------------------------------------
# Compare passwd file with
# phone listing, change desc
# in passwd file, send output to /tmp
#-------------------------------------
BEGIN {
  FS=":"
}
{
 pline=$0
 pwdline=$5
 chflag=0
 len2=0

 while ((getline pname < "/tmp/list1.txt") && (chflag==0))
       {
       addrline=pname;
       len2 = length(addrline);
       addrline2 = substr(addrline,1,len2 - 4 );
       if ((index(pwdline,addrline2) > 0) && (len2 > 5))
          {
          pline=$1 ":" $2 ":" $3 ":" $4 ":" pname ":" $6 ":" $7 ;
          chflag=1 ;
          }
       }
 close("/tmp/list1.txt") ;

 print pline ;

 if (chflag==0)
    {
    system("echo " "\"" pline "\"" " >> /tmp/list2.txt") ;
    }
 else
    {
    modcmd = "zzz" addrline "zzz " ;
    system("echo " "\"" "usermod -c " modcmd $1 "\"" ">> /tmp/list3.txt") ;
    }

}

# to call the above awk program, use
cat /etc/passwd | nawk -f passwdmod.awk
# this final step puts the quotes in the usermods file
cat /tmp/list3.txt | sed "s/zzz/\"/g" > /tmp/usermods

Finding files

 A handy script for finding files quickly. 
#!/usr/bin/ksh

if test $# -lt 1
then
   echo " "
   echo "usage:"
   echo "------"
   echo "find2 "
   echo " "
   echo " "

   exit
fi

echo " "
echo "Searching file systems ..."
echo " "

find $PWD -name "$1" 2>/dev/null

Moving/copying files

 A handy script for changing file extensions. The source could be modified to copy and move files. 
#!/usr/bin/ksh
#-----------------------------
#  File Extension Changer
#  Parms:  extension, new-extension
#-----------------------------
if test $# -lt 2 ; then
   echo " "
   echo "useage: "
   echo "chxtn source-xtn dest-xtn"
   echo " "
   exit
fi

for fname in *.$1 ; do
    echo "Moving: " $fname
    newname=${fname%%.*}

    if test -f $fname ;  then
      mv $fname $newname.$2
    fi
done

Deleting files

 This script deletes the first n# files in a directory, useful for numbered log files. 
#------------------------------------------
#  Parms:  Directory, wildcard, # of files to delete
#------------------------------------------

if test $# -lt 3
then
   echo " "
   echo "usage:"
   echo "------"
   echo "rmfiles   <# of files>"
   echo " "
   echo " "

   exit
fi

if test ! -d $1 ; then
   echo " "
   echo " Invalid path: "
   echo $1
   echo " "

   exit
fi

cd $1

i=1


for filename in $2 ; do

  echo $filename
  rm $filename

  i=`expr $i + 1`
  if test $i -gt $3 ; then
     cd
     exit
  fi
done

Sending mail

 
#!/usr/bin/ksh
# send an e-mail, via shell script
rmail jsmith@mydomain.com << endmsg2
From sjones 10:00am remote from servername

Hi Jim -

Send an e-mail if we're still on for lunch at
12:30 ...

Steve

endmsg2


#!/usr/bin/ksh
#-------------------------------------
#  Send big mail
#-------------------------------------
if test $# -lt 4
then
   echo " "
   echo "usage:"
   echo "------"
   echo "bigmail    "
   echo "(type quotes around message if more than one word)"
   echo " "
   echo " "

   exit
fi

print From $2 3:00pm remote from $3 > /tmp/r1.txt
print " " >> /tmp/r1.txt
banner $4 >> /tmp/r1.txt
print '.' >> /tmp/r1.txt
rmail $1 < /tmp/r1.txt
rm /tmp/r1.txt
















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email ... 
js99@rocket99.com






Copyright 1998-2000 © Citisoft, Inc. All Rights Reserved.