Shell Programming and Scripting

why does this not work, confused

Code:

#!/bin/ksh
x="x"
echo "Enter a name: "
read NAME
while [$NAME != $x]
do
echo $NAME
echo
if [$NAME == $NAME]
then
echo ":"
else
echo $NAME
fi
echo
echo "Enter a Name: "
read NAME
done
de

There has to be a space after [ and before ], like so:

Code:

Code:

 [ $NAME != $x ]

Code:

if [ $NAME == $NAME ]

Now, this is confusing to me, when would $NAME not be equal to $NAME?
What are you confused about it?

Im trying to understand how to do something I'm working on at work

I'm trying to read a users name from input store it in name, then enter a while loop as long as name is not equal to x, then if name is equal to name do nothing, but if name is != name do something, exit if statement, check name variable if not x continue looping, if x end program. Does that make sense?

---------- Post updated at 09:50 PM ---------- Previous update was at 09:35 PM ----------

so now code is

Code:

#!/bin/ksh
x="x"
echo "Enter a name: "
read NAME
while [ "$NAME" != "$x" ]
do
echo $NAME
echo
if [ $NAME == $NAME ]
then
echo ":"
else
echo $NAME
fi
echo
echo "Enter a Name: "
read NAME
done

When I view the output it keeps asking for a name, and is ignoring the x if name is x, and looks like it is infinite looping. Why?

> Does that make sense?
Mostly, until you get here:
>then if name is equal to name do nothing, but if name is != name do something

I am trying to let you know that name will never be anything else but name. Even if you change the content of variable $NAME, it will always be true, therefore, it does not make any logical sense (in the technical sense).

Now:
[ $NAME != $x ] That makes sense, $NAME can contain something different that $x, but $NAME would never contain something different to compare.
You need to create another variable containing another name you want to compare.

Hope it helps.

We have undestood that, but: "if name is equal to name" is true regardless of the value of "name", so the condition is moot. You could have written "if 1 equals 1" for the same effect.

For any if-else-decision to make sense there must be a condition which is sometimes true, sometimes not true. If it is always true or always not true, then you do not need a condition at all. If i say to you "if the time is in the evening then go to sleep, otherwise get up" there is a condition (what the time is) and sometimes this will be "in the evening", sometimes not, resulting in "get up" sometimes and in "go to sleep" otherwise.

What you do is "if the time is any time then get up" - but you do not need to refer to the time at all in such a case, because its value would be irrelevant anyways.

I hope this helps.

bakunin

ok, let me ask you this then, lets say I enter a users name, I read in the value, while name is not equal to x I do something, I then grep a file to search if the value of name exists in there, if so I don't want it to do anything, if not, then I want it to do something, then exit the if block go back where I left off in while loop, check value of name variable, if name is not x continue looping, once name is an x end program. How would I do that then? In other words how do you compare the value of name to value of name that I grep from another file?

Just as an idea, not meant to be your personal solution.

Code:

#!/bin/ksh

x="x"
echo "Enter a name: "
read NAME

while [ "$NAME" != "$x" ]; do
    
    if [ ! $(grep "$NAME"  filename) ]; then
        echo "$NAME is not found in filename"
    fi

    echo "Enter a name: "
    read NAME
done