How To Unix For Loop 1 to 100 Numbers

POSIX syntax

The syntax is as follows using while loop to count 1 to 5 numbers:

#!/bin/sh
i=0
while [ $i -ne 5 ]
do
        i=$(($i+1))
        echo "$i"
done

For bash shell replace the line:

#!/bin/sh

With:

#!/bin/bash --posix

Ksh For Loop 1 to 100 Numbers

#!/bin/ksh
# Tested with ksh version JM 93t+ 2010-03-05
for i in {1..100}
do
 # your-unix-command-here
 echo $i
done

We can use while loop too:

#!/bin/ksh
i=1
while [[ $i -lt 1000 ]] ; do
   # your unix command here #
   echo "$i"
  (( i += 1 ))
done

C-like for loop syntax for ksh93/bash/zsh

The syntax is as follows:

#!/bin/ksh93
for ((i=1; i<=20; i++))
do
    # Unix command here #
    echo "$i"
done

Bash For Loop 1 to 100 Numbers

#!/bin/bash
# Tested using bash version 4.1.5
for ((i=1;i<=100;i++)); 
do 
   # your-unix-command-here
   echo $i
done

Dealing With Older KSH88 or Bash shell

The above KSH and Bash syntax will not work on older ksh version running on HP-UX or AIX. Use the following portable syntax:

#!/usr/bin/ksh
c=1
while [[ $c -le 100 ]]
do 
  # your-unix-command-here
   echo "$c"
   let c=c+1
done

Here is script that is tested with older version of KSH running on Sun Solris and HP-UX/AIX:

#!/bin/ksh
i=1
echo "Counting from 1 to 10: "
while (( $i <= 10 ))
do
   echo "$i"
  (( i=$i+1 ))
done

Outputs:

Counting from 1 to 10: 
1
2
3
4
5
6
7
8
9
10

Say hello to seq for iterating through a range of ints in ksh?

The following command displkay numbers from FIRST to LAST, in steps of INCREMENT:
seq FIRST LAST
seq FIRST INCREMENT LAST
Iterating through a range between 1 to 10 in ksh is as follows:
seq 1 10
To increment value by 2:
seq 1 2 10
For example:

#!/bin/ksh
for n in `seq 1 100`
do 
  echo "Hello, $USER. [$n]"
done

The seq command works regardless of shell version and we can use variables too:

START=5
END=10
for i in $(seq $START $END)
do
   echo "Doing something with $i ..."
done

Doing something with 5 ...
Doing something with 6 ...
Doing something with 7 ...
Doing something with 8 ...
Doing something with 9 ...
Doing something with 10 ...

Conclusion

We learned various methods to count numbers between 1 to 100 when using KSH, bash, sh and other shell running on Linux or Unix-like systems. See man pages:
$ man ksh
$ man bash
$ man sh