Basic korn shell notes

korn shell notes
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Commands:
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   # - comment line
   >  - output to a file
   >>  - append to a file
   <  - input from a file
   <<!  - redirect from inside a shell script until next !
   VAR=value - assigns value to shell variable
   echo "$VAR did something" - $ in front of variable name prints value
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Special Variables:
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   $$ - current process id PID
   $* - all command line arguments
   $# - number of command line arguments
   $0 - shell program name
   $3 - third argument on command line
   $? - return code of last command 0 is usually successful
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Control Structures:
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end of if is if spelled backwards
elif is else if
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   if [ $VAR = XXX ]
   then
      echo "do something if true"
   elif [ -f $FILE -a -r $FILE ]
      echo "$FILE is a file and is readable"
   else
      echo "do something else if not true
   fi
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   if VAR is null then the above if gives syntax error
   if [ "$VAR"x = "XXX"x ] will fix problem
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   read FILE_NAME - does input in variable
   TODAY=`date +"%y/%m/%d %A"` - output date command into variable TODAY
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end of case is case spelled backwards
options on case statements do pattern matching
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   case $FILE in
      /DW/*)
          echo "is a program"
          ;;
      /xfer*)
          echo "is data"
          ;;
      *)
          echo "* is always true"
          ;;
   esac
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   while [ -f $FILE ]
   do
      echo "something if FILE is a UNIX file"
      break - will break out of loop
   done
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pipe from command
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   ls dw* |
   while read FILE_NAME
   do
      grep mailx $FILE_NAME
      if [ $? -eq 0 ]
      then
         echo "$FILE_NAME has mailx in it"
         rm $FILE_NAME
      fi
   done
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redirect input from file
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   while read FILE
   do
      echo $FILE
   done <inputfile
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   for FILE in $*
   do
      # FILE values come from command line arguments
      rm $FILE
   done
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true false statements
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spaces around [ and ] are absolutely neccessary
also spaces around <>=!= are absolutely neccessary
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test -d /dirname   is same as   [ -d /dirname ]
-f checks for file
-d checks for dir
-r is file readable
-x is file executable
-eq numeric test
-gt numeric test
-ge numeric test
-lt numeric test
-le numeric test
-a and
-o or
!= not equal
<> also not equal
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Example:
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if [ $# -lt 3 ]
then
   echo "Usage: $0 sys dir file"
   exit 3
fi
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UNIX commands:
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   lp -d cc099_hp4si28 filename - prints file
   cat file1 file2 file3 >newfile - combines file1,2 and 3
   tail -3 file1 - displays last 3 lines of file1
   head -4 file1 - displays first 4 lines of file1
   cp file1 file2 - copies file1 to file2
   cp file1 dir - copies file1 into dir
   mv file1 file2 - renames file1 to file2
   mv file1 file2 file3 dir - moves files 1 thru 3 into dir
   wc -c file1 - counts chars in file1
   wc -l file1 - counts lines in file1
   ls -l & - runs ls -l in background
   ls -l | mailx -s"subject" userid - mails results of ls command
   mailx -s"testing" kyennara - mails message to kyennara (^d stops)
   df -k - disk free space in 1K blocks
   bdf - nicer version of abpve
   du -s -k /DW - disk usage summary of files in /DW in 1K blocks
   grep regexpression file1 file2 - will print lines that match exp
   grep -v regexpression file1 - will print lines that do not match exp
   grep -i regexpression file1 - will ignore case
   fgrep - fast grep
   egrep - extended grep
   egrep -f regexpfile file1 - will do multiple regexp from regexpfile
      the expressions are line1 or line2 or line3
   date | cut -c4-7 - cut columns 5 thru 8 month from date command
   date | cut -d" " -f4 - cut field 4 time from date command
   TABLE=`echo "$TABLE          " | cut -c1-10`
      - will force TABLE to be 10 chars long
   grep $LOGNAME /etc/passwd | cut -d":" -f3 - cuts UNIX group id
   pr -t -s -m file1 file2 - will print file1 and file2 side by side
   basename $FILE_NAME - will print just the file name not the path
   dirname $FILE_NAME - will print the dir the file is in
   hostname - prints the UNIX machine name
   set - $LINE - will parse LINE into $1 $2 $3 etc
   ROWS_NOT_LOADED=`expr $ROWS_NOT_LOADED + $ROWS` - will do math
   exit 3 - will exit with return code of 3
   who - list users
   who -a - lists all fields
   ps -ef - lists process table
   ps -ef | grep $LOGNAME - lists my process table
   ps -f - lists my process table (better method)
   ps -ef | grep bawillia - lists Bruce's process table
   ps -fu bawillia - lists Bruce's process table (better method)
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find all the files with yy and not yyyy
if grep.list has yy[^y]
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   find . -type f -exec egrep -n -f grep.list {} /dev/null \;
   USER=kduke
   ps -fu $USER | grep -v PID |
   while read LINE
   do
      set - $LINE
      PID=$2
      # will kill all $USER processes
      kill $PID
   done
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Notes:
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   Normally ksh is setup to do vi commands on history.
   ESC puts you in vi mode.
   Arrow keys will not work.
   Use h,j,k,l for left,down,up and right.
   /^vi will find your last vi command.
   dd will create a blank line then hit return to get out of vi mode.
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