[SOLVED] If .. then... else .. fi

jv2112 · 09-04-2010, 09:23 AM

I am trying to learn if , then , else statements and I can't get it correct. I have written a basic script below and from what I am reading it looks correct but it does not go to the second option (else) if the first argument is not true.

Any help would be appreciated.

Quote:

#! /bin/bash

echo "Do you want to enter the pit ?"
read answer

if [ $answer=yes ]; then

echo " Good Luck !"
else
echo " Chicken ....."
fi

PS -> This is not homework question. (Kinda sounds like one) Not even in school. Just trying to learn...

jay73 · 09-04-2010, 09:31 AM

if [ $answer = yes ]

You need the spaces to make a valid comparison.

Note: you may want to use == instead of =. It helps to avoid that sort of confusion.

jv2112 · 09-04-2010, 10:06 AM

white space = Root of all evil

Thanks for the help.

grail · 09-04-2010, 10:31 AM

Please mark as SOLVED if you have a solution.

colucix · 09-04-2010, 10:44 AM

Even better in bash and ksh you might use the extended test command, with double square brackets. Among other advantages, it prevents logic errors when the value of the variable is null and you missed the double quotes around it. Example:

Code:

if [[ $answer == yes ]]
then
  echo something
fi

For a discussion about the extended test command, you can take a look at the Advanced Bash Scripting Guide, here.

slakmagik · 09-04-2010, 02:47 PM

Quote:

Originally Posted by jay73

if [ $answer = yes ]

You need the spaces to make a valid comparison.

Note: you may want to use == instead of =. It helps to avoid that sort of confusion.

In some shells that will produce something along the lines of '[: ==: unexpected operator'. Generally, tests should be written '[ foo = bar ]' or (better), if the shell is capable, as colucix says, '[[ foo == bar ]]'.

jay73 · 09-04-2010, 05:15 PM

No doubt. But even the "echo" command is not as portable as many seem to assume; for maximum portability C-like printf should be used...