Workshop

From Chania-LUG Wiki

Επιστροφή

Bash Shell as a Programming Language

• if, elif, for, for, while, until, case, select
• Conditions
• Variables (Μεταβλητές)
• Lists (Λίστες)
• Functions (Συναρτήσεις)
• Build-in commands
• Here Documents

---

Ας λερώσουμε τα χέρια μας (Level 1)

-Goals: #!, #, Commands, make executable, ', ", \.

#! /bin/bash

# This is a silly script
echo "hello, I'm your first script"
echo "What do you think?"

---

Level 2

Ας γράψουμε ένα script που να δέχεται ένα χρήστη και να υπολογίζει το μέγεθος που έχει ο home του κατάλογος. -Goals: Variables, Special Variables, Conditions, if, test-[

#! /bin/bash
# LGU v3 of course...

# This script calculates and prints the User's home usage.

if test $# -lt 1  #test --> [
then
   echo "You have to specify at least one user."
   exit  #exit 1
fi

cd /home/$1
SPACE=$(du -s | cut -f 1)
echo "$1 is using $SPACE kilobytes."
exit # exit 0

---

Level 3

Ας το τροποποιήσουμε ώστε να δέχεται παραπάνω από ένα χρήστη.

-Goals: exit status, loops - for, stdin(out) vs exit

#! /bin/bash
# LGU v3 of course...

# This a second script calculates and prints the User's home usage.

if [ $# -lt 1  ]
then
   echo "You have to specify at least one user."
   exit 1
fi

for SOMEONE in $@
do
   cd /home/$SOMEONE
   SPACE=$(du -s | cut -f 1) # du -s 2>/dev/null
   echo "$SOMEONE is using $SPACE kilobytes."
done
exit 0

---

Level 4

Ας το κάνουμε μόνο για τον root και χωρίς να παίρνει παραμέτρους.

-Goals: more in to loops, lists, blocks, check exit status

#! /bin/bash
# LGU v3 of course...

# This a third script calculates and prints the User's home usage.

# check if /etc/passwd exists (hahahaha)
[ ! -f /etc/passwd ] && { echo "Ouaou!!!!"
                          exit 1
                        } 

if [ "$(id -u)" != "0" ] # root login check
then
   echo "Go try to login as root and come again!!!"
   exit 1
fi

for SOMEONE in $(cat /etc/passwd | grep '/bin/bash' | cut -d ':' -f 1) #Φυσικά κάτω από ARG_MAX
do
   cd /home/$SOMEONE
   if [ $? -ne 0 ]
   then
      echo "Can not read $SOMEONE\'s home directory"
      continue
   fi 
   SPACE=$(du -s /home/$SOMEONE 2>/dev/null | cut -f 1) #περιττό 2>/dev/null
   echo "$SOMEONE is using $SPACE kilobytes."
done

exit 0

---

Level 5

Και τώρα πια που μάθαμε και κάτι, ας του βάλουμε και παραμέτρους

#! /bin/bash
# LGU v3 of course...

# This a third script calculates and prints the User's home usage.

SEARCH_USERS="/tmp/tmpfile"
true > "$SEARCH_USERS"

# check if /etc/passwd exists (hahahaha)
[ ! -f /etc/passwd ] && { echo "Ouaou!!!!"; exit 1; } 

if [ "$(id -u)" != "0" ] # root login check
then
   echo "Go try to login as root and come again!!!"
   exit 1
fi

if [ -z "$1" ]
then
   echo "Error. Type $0 --help"
   exit 1
fi

while [ -n "$1" ] # [ ! -z xxx ]
do
   case "$1" in
      -a)
         cat /etc/passwd | grep '/bin/bash' | cut -d ':' -f 1 > "$SEARCH_USERS"
         shift
      ;;
      -u)
         echo "$2" >> "$SEARCH_USERS"
         shift; shift
      ;;
      *)
         echo "Error. Type $0 --help"
         exit 1
      ;;
   esac
done

IFS=$'\n'
for SOMEONE in $(cat $SEARCH_USERS) #Φυσικά κάτω από ARG_MAX
do
   cd /home/$SOMEONE 2>/dev/null
   if [ $? -ne 0 ]
   then
      echo "Can not read $SOMEONE's home directory"
      continue
   fi 
   SPACE=$(du -s /home/$SOMEONE 2>/dev/null | cut -f 1) #περιττό 2>/dev/null
   echo "$SOMEONE is using $SPACE kilobytes."
done

rm -f "$SEARCH_USERS"
exit 0

---

Level 6 - Are you nuts?

Πάμε να βάλουμε συναρτήσεις και SIGNALS? Αχά...

#! /usr/bin/env bash
# LGU v3 of course...

# This a third script calculates and prints the User's home usage.

SEARCH_USERS="/tmp/tmpfile"

#-------------------------------------
# initialization routine
init ()
{

  true > "$SEARCH_USERS"

  # check if /etc/passwd exists (hahahaha)
  [ ! -f /etc/passwd ] && quit "Ouaou!!!!" 1

   # root login check
   [ "$(id -u)" != "0" ] && quit "Go try to login as root and come again!!!" 1

   IFS=$'\n'
}

#--------------------------------------
# usage:
# quit "message" "exit status"
quit ()
{
   echo "$1"
   rm -f "$SEARCH_USERS"
   exit "$2"
}

#--------------------------------------
# Usage:
# par_parser $@
par_parser ()
{
   [ -z "$1" ] && quit "Error. Type $0 --help" 1
   while [ -n "$1" ] # [ ! -z xxx ]
   do
      case "$1" in
         -a)
            cat /etc/passwd | grep '/bin/bash' | cut -d ':' -f 1 > "$SEARCH_USERS"
            shift
         ;;
         -u)
            echo "$2" >> "$SEARCH_USERS"
            shift; shift
         ;;
         *)
            quit "Error. Type $0 --help" 1
         ;;
      esac
   done
}



#-----------------------------------------------------------
#                   main routine
trap 'quit "Process terminated..." 0' SIGINT SIGTERM SIGHUP

init
par_parser $@

for SOMEONE in $(cat $SEARCH_USERS)  #Φυσικά κάτω από ARG_MAX διορθώνεται στο επόμενο level.
do
   cd /home/$SOMEONE 2>/dev/null  #Είπαμε, αυτό
   if [ $? -ne 0 ]
   then
      echo "Can not read $SOMEONE's home directory"
      continue
   fi 
   SPACE=$(du -s /home/$SOMEONE 2>/dev/null | cut -f 1) #ή αυτό
   echo "$SOMEONE is using $SPACE kilobytes."
done

quit "" 0

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