Timed read Prompt 1

[Michael42]

Hello,

In a Bourne shell script if I am prompting a user using a read command, if the user does not enter anything for a set number of seconds (say 15) how can I "escape" the read prompt?

Thanks,

Michael42

 

[SamBones]

This should work...

#!/bin/sh

OLDSTTY=`stty -g`

stty -icanon min 0 time 150

echo "Enter something: \c"

read TEST

stty "${OLDSTTY}"

echo
echo "TEST=${TEST}"

Keep in mind there is a limit to how long some terminals can wait. I think something like 25 seconds or so.

Hope this helps.

 

[p5wizard]

If you want to do that in Korn shell, you can't use read directly for timed reads as ksh ignores your modified stty settings when reading from terminal.

However this works:

#!/bin/ksh

OLDSTTY=`stty -g`
stty -icanon min 0 time 150 # read at least zero chars
                            # wait up to 15s for user to type something

echo "Enter something: \c"
line | read TEST junk       # reads the users input line (possible null string)
                            # divides the line: first word goes into TEST variable
                            # the rest of the line is ignored (junk variable) 

stty "${OLDSTTY}"

echo
echo "TEST=${TEST}"

HTH,

p5wizard

 

[SamBones]

He said he was writing a Bourne shell script so I gave him a Bourne shell solution.

And it does work in the Korn shell on my system on Solaris 8.

 

[p5wizard]

I know he specified bourne, I just wanted to try it out in ksh on AIX and it didn't work, so I tried to find out why - that's all.


HTH,

p5wizard

 

[p5wizard]

Note: if you put your shell in "set -o vi" or some other history editing mode, ksh overrides whatever stty mode you set, and your bourne shell solution won't work in Korn shell.

Also you might want to set a trap for some signals in order to reset the stty settings or risk being logged out after the timeout expires when you exit the script without first running stty ${OLDSTTY} ...

#!/bin/sh

OLDSTTY=`stty -g`

trap "stty ${OLDSTTY};exit" 0 1 2 3 15

stty -icanon min 0 time 150

echo "Enter something: \c"

read TEST

stty "${OLDSTTY}"

echo
echo "TEST=${TEST}"

HTH,

p5wizard