If then else in bash is not very difficult. However, there is something that can cause problems:

Please note the spacing inside the brackets! It won't work without!

string comparison

simple example:

 


            #!/bin/bash

            MYVAR="hello"
            if [ "$MYVAR" = "hello" ]; then
               echo "true"
            else
               echo "false"
            fi


 

integer comparison

A is equal B - a simple example: 

#!/bin/bash

A=1

B=2

if [ "$A" -eq "$B" ]; then
   echo "$A is queal $B"
else
   echo "$A is not equal $B"
fi



 

 

A is not equal B - a simple example: 


#!/bin/bash

A=1

B=2

if [ "$A" -ne "$B" ]; then
   echo "$A is not queal $B"
else
   echo "$A is equal $B"
fi



 

 

A is greater than B - a simple example: 


#!/bin/bash

A=2

B=1

if [ "$A" -gt "$B" ]; then
   echo "$A is greater than $B"
else
   echo "$A is not greater than $B"
fi



 

 

A is less than B - a simple example: 


#!/bin/bash

A=1

B=2

if [ "$A" -lt "$B" ]; then
   echo "$A is less than $B"
else
   echo "$A is not less than $B"
fi



 

 

A is less than or equal to B - a simple example:

 

#!/bin/bash

A=1

B=2

if [ "$A" -le "$B" ]; then
   echo "$A is less than or equal to $B"
else
   echo "$A is greater than $B"
fi

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Comments (1)

• |122.174.122.xxx |2010-12-25 18:23:22 kannan
  Hi,
  I am new to Linux programming.
  
  the above examples looks good thanks very much
  
  From
  kannan.R
  • 0
  • 0

  Reply | Quote

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