Linux shell loop example

For Loop example

For Loop Syntax:

for VARIABLE in 1 2 3 4 5 .. Ndo         command1         command2         commandNdone
 
#!/bin/bashfor i in 1 2 3 4 5doecho "Welcome $i times"done

Bash version 3.0 +Version
#!/bin/bash for i in {1..5}do   echo "Welcome $i times"done
Bash version 4Version 
#!/bin/bashecho "Bash version ${BASH_VERSION}..."for i in {0..10..2}  do     echo "Welcome $i times" done
Syntax example with "seq" command
#!/bin/bashfor i in $(seq 1 2 20)do   echo "Welcome $i times"done
Three expressions of the for Loop
Syntax:
for (( EXP1; EXP2; EXP3 ))do         command1         command2         command3done
Example:
#!/bin/bashfor (( c=1; c<=5; c++ ))do         echo "Welcome $c times..."done
Effect:
Welcome 1 timesWelcome 2 timesWelcome 3 timesWelcome 4 timesWelcome 5 times
For infinite loop
#!/bin/bashfor (( ; ; ))do   echo "infinite loops [ hit CTRL+C to stop]"done
Break Condition Statement
for I in 1 2 3 4 5do  statements1      #Executed for all values of ''I'', up to a disaster-condition if any.  statements2  if (disaster-condition)  then         break                #Abandon the loop.  fi  statements3          #While good and, no disaster-condition.done
The following shell script stores all the files in the/etc directory. The for loop will discard the file found in/etc/resolv. conf.
#!/bin/bashfor file in /etc/*do         if [ "${file}" == "/etc/resolv.conf" ]         then                 countNameservers=$(grep -c nameserver /etc/resolv.conf)                 echo "Total  ${countNameservers} nameservers defined in ${file}"                 break         fidone
Continue Condition Statement
for I in 1 2 3 4 5do  statements1      #Executed for all values of ''I'', up to a disaster-condition if any.  statements2  if (condition)  then         continue   #Go to next iteration of I in the loop and skip statements3  fi  statements3done
Use this script to back up all file names specified in the command line. If. The bak file exists. It skips the cp command.
#!/bin/bashFILES="$@"for f in $FILESdo        # if .bak backup file exists, read next file         if [ -f ${f}.bak ]         then                 echo "Skiping $f file..."                 continue  # read next file and skip cp command         fi        # we are hear means no backup file exists, just use cp command to copy file         /bin/cp $f $f.bakdone