Bourne Shell Programming Input and Output

[Chua Wen Ching]

I need some help here and i not sure whether bourne shell programming can do it or not. I am using hp-ux 10.20.
The output:
echo "Enter number : [0000]"
read inputNumber

Just assume that the 4 zeros inside the bracket is the input that i want to enter. Example, 1111 or 2341. But if follow the source code on top, i can enter more than 4 numbers maybe 12345 or 99999. How to make it only accept 4 numbers or alphabets on the standard output (displayed on the monitor) and standard input (key in using keyboard)? Thank you.

[Trond Haugen]

I believe that requiers som programming in C or som other language..

Regards,
Trond

[H.Merijn Brand (procura]

# cat xx.sh
#!/usr/bin/sh

ans=x
while `perl -e"exit '$ans'=~m/^\d{1,4}$/"` ; do
echo "Gimme a number [0000]\c"
ans=`line`
done
echo "You entered a valid number: $ans"
# sh xx.sh
Gimme a number [0000]a
Gimme a number [0000]12345
Gimme a number [0000]99
You entered a valid number: 99
#

[Jean-Luc Oudart]

Without perl :
#!/bin/sh

while [ true ] ; do
unset ans
echo "Gimme a number [0000]\c"
ans=`line`
anslen=` echo $ans | wc -c `
# echo "ans " $ans $anslen
if [ $anslen -gt 1 -a $anslen -lt 6 ]; then
break
fi
done
echo "You entered a valid number: $ans"

Gimme a number [0000]
Gimme a number [0000]12345
Gimme a number [0000]123
You entered a valid number: 123

As this is for up to 4 digits or alphabets

Jean-Luc

[harry d brown jr]

It's perl time!

live free or die
harry

[Shannon Petry]

You can not grab a spefic amount of characters in any of the standard shells (borne, korn, csh, tcsh, bash, bash2, etc...).

You need to either write your own little C code (very short code) or use perl (shorter code)

Regards,
Shannon

[Ian Dennison_1]

Unfortunately POSIX Shell is not as all-singing and all-dancing as other structured programming languages.

Best lower your expectations rather than spend ages working around them!

Share and Enjoy! Ian

[James R. Ferguson]

Hi:

Here's another way, using shell features:

#!/usr/bin/sh
echo "enter a number"
read X
if [ -z "$X" -o `expr length "$X"` -gt 4 -o `expr "$X" : '[0-9,\-]*'` -ne `expr
"$X" : '.*'` ]
then
echo "not a valid number!"
else
echo "ok, it's a good number!"
fi
exit 0

The above piece of code will verify that the input read isn't null; consists only of the digits 0-9; and is only one to four digits in size.

Regards!

...JRF...

[Chua Wen Ching]

Thank you for posting up the sample source codes on handling the standard input. Thanks a lot. But i had the problem which i will show below:

1st example,
Enter a number: [____] (4 numbers)

2nd example,
Enter a number: [1234]

3rd example,
Enter a number: [12345 (the bracket is overwritten)

4th example if i backspace,
Enter a number: [1234 (the bracket is lost)

How to maintain the 4 digit to be entered to the system? Only allowed 4 and not more than that. If i press additional key

5th example,
Enter a number: [1234]

--if i press 8

6th example,
Enter a number: [1238]

As you can see the bracket is not overwritten and the user can only enter 4 numbers only. Any idea on this? Can bourne shell do something like this? Thanks for your posting and your help.

[Chua Wen Ching]

Oops...i forget to read the messages properly.

To Shannon Perty
-----------------
You can not grab a spefic amount of characters in any of the standard shells (borne, korn, csh, tcsh, bash, bash2, etc...).
You need to either write your own little C code (very short code) or use perl (shorter code)

Can you show me an example of c or perl code that enable to grab a specific amount of characters? If i write something in C or Perl, can i integrate that script into my bourne shell application.

Ian Denisson
-------------
Thank you for your advice and i will try to bear that in mind.

Anyway thanks for everyones help.

[Chua Wen Ching]

Really no solutions? Anyway thanks for your help.

[H.Merijn Brand (procura]

What's wrong with my answer? It is easy to tweak it to stay within the brackets.

Jean-Luc copies my answer - removes the perl part - and gets five point, though we still don't know what is wrong with either.

[Chua Wen Ching]

Dear procura, i had tried your sample code but it only displays:
Standard Output
---------------
Gimme a number [0000]1234
Gimme a number [0000]12345
Gimme a number [0000]12
..
keep looping
(i did not see the message You entered a valid number ...)
Did you miss out anything?

But what i want is:

Gimme a number [0000] -> 4 numbers only
Gimme a number [12 ] -> i enter 12
Gimme a number [0123] -> i enter 123
Gimme a number [1234] -> i enter 1234
Gimme a number [1235] -> i enter 12345

(i want to enter my input inside the bracket rather than outside the bracket, i know how to position the cursor, but if i enter more than 4 numbers, it overwrite the ])

Base on you reply, It is easy to tweak it to stay within the brackets? Can you explain to me clearly please. Maybe some sample codes. I don't understand your explanation earlier. Anyway thanks for replying. Sorry for the marks.

[Wodisch]

Hi,

if you really want to do this in "shell" then you'll have to use something like this:

#!/usr/bin/'sh
# read a 4-digit number from stdin

digit() {
d=$(dd bs=1 count=1 2>/dev/null)
echo $d
}

old=$(stty -g)
stty raw -echo -echoe -echok
number="xxxx"
while [ "$number" -lt "0000" -o "$number" -gt "9999" ]; do
echo "Enter number: \c"
d1=$(dd bs=1 count=1 2>/dev/null); echo "$d1\c"
d2=$(dd bs=1 count=1 2>/dev/null); echo "$d2\c"
d3=$(dd bs=1 count=1 2>/dev/null); echo "$d3\c"
d4=$(dd bs=1 count=1 2>/dev/null); echo "$d4"
number="$d1$d2$d3$d4"
done
stty $old
echo "Your number is $number"

HTH,
Wodisch

[Chua Wen Ching]

Dear Wodish, when i run your script i saw an error:
Stout
-----
script interpreter "/usr/bin/'sh" not found
Script intepreter "/usr/bin/'sh" not found
sh: readnumber.sh not found
(i name your script into readnumber.sh)

So i remove the ' to become /usr/bin/sh
Is it okay to remove it. I think it shouldn't be a problem.

But after i run again your script i saw this error:
stout
-----
readnumber.sh[12]: xxxx: The specified number is not valid for this command.
Your number is xxxx

I analyze your script i notice that can i really compare xxxx with numbers. So i try to change number=1234 or number=11111. But it did not go through the loop.
Can you really run this script properly in unix as i am using HP-UX 10.20? Thank you for your help.

[Chua Wen Ching]

Dear Wodisch, The script can work already as i assign number=-1. But i do not understand why you assign number="xxxx"? But i feel there is some problem right here with the standard output.

Stout
-----
Enter number : 1234 (after enter 4 automatic display)
Your number is 1234

But in between the first message and 2nd message there are a lot of spaces.

Stout
------
Enter number : 1234 (spaces) -line 1 - Message 1
(spaces) Your number is 1234 - line 2 - Message 2

1) Can i remove all this spaces so that when i display my result the message 2 will be on the left side.
Expected stout
--------------
Enter number : 1234
Your number is 1234

2) When i just press 4 it just automatic display the message 2? Can i pause it before i display the message 2? Example

Expected stout
---------------
Enter number : 1234 (cursor blinking in 4 except i press enter to move to message 2)
Enter number : 1235 (if i enter 5 it will replace 4, i feel like this looks more realistic).

3) What does this command means?
a. stty raw -echo -echoe -echok
b. stty -g

As i know stty -echo is to hide the input that you enter. What is raw and -echoe and -echok for? stty -g is for what purposes?

Anyway thanks for your help Wodisch. It really help me a lot.

[Chua Wen Ching]

Dear Wodisch, i see errors when i press the backspace, space bar and enter key. Examples:

Example 1 (stout)
-----------------
Enter number : 12 + (2 spaces)
Your number is 12

(can i type 12 and press enter to display the second message)

Example 2 (stout)
-----------------
Enter number : 12 + (2 enters)
Your number is 12

(can i only press 1 enter rather than 2 times to see message 2)

Example 3 (stdout)
------------------
Enter number 12 + (2 backspaces)
readnumber.sh[12]: 12^H^H: Syntax error
Your number is 12

(can i press backspaces if i key in the wrong number to modify the new value, but still limits to 4 characters)

Before:
Enter number : 132
--after backspace 2 times
After:
Enter number : 122 (new value)

Example 4 (stdout)
------------------
Enter number : (4 backspaces)
The cursor is below character r
readnumber.sh[12]: ^H^H^H^H: Syntax error

(Is it possible if i press backspace without entering any characters, it will not move back and erase my 1st message)

Before:
Enter number : _ (_ = cursor)
--after press backspace
After:
Enter number : _ (still at the same

It sound confusing here but i do not know whether bourne shell programming can do that or not? Any bourne shell sample codes to aid me thank you.

[Chua Wen Ching]

No other solutions? Is it really that bourne shell does not have the capabilities to do that. Anyway thank you.

[H.Merijn Brand (procura · Accepted solution]

The bourne shell ain't no glossy programming environment :) It's the most basic interface the user has to the system.

You *do* have to use C/perl/... to get into more shiny processing, and use libraries or modules to do extensive user interaction. C can be used to build user interfaces that adopt to X11, Motif, KDE, Qt, or any `standard' or well documented graphic frontend. Perl has a wide range of modules that interface to standard graphic environmets, like Perl/Tk and Perl/Gtk.

[Chua Wen Ching]

The problem here is my org unix does not have perl/tk and have an old perl interpreter 4.0. I had some problems whether C can work well with bourne/Posix scripting? Is there any C and Bourne/Posix sample scripts (both integrated) to do the processing? Thank you.

[Michael Tully]

You can get perl version 5.6.0 for 10.20 at the following link ready for installation.

http://www.webmin.com/hpux.html

[Chua Wen Ching]

I had send an appeal so that my org can update to perl5.6.0. Thanks for the link. How about the C and Bourne/Posix integration? Thank you.

[Jean-Louis Phelix]

Hello,

Just for fun ... with this one you can use backspace and can't enter more than $MAX chars (this could also be a parameter). I also added a filter to accept only digits and '.'.

Regards,

Jean-Louis.

#!/usr/bin/sh

beep()
{
VAR=
echo '\007''\c'
}

STRING=$1
LEN=$(expr "$1" : ".*")
MAX=4
OLDSTTY=$(stty -g)
FORMAT1="\rEnter number ["
FORMAT2="${FORMAT1}%${MAX}s]"
VAR=
while [ -z "$VAR" ]
do
printf "$FORMAT2" " "
printf " "
printf "$FORMAT1$STRING"
stty raw -echo -echoe -echok
VAR=$(dd bs=1 count=1 2>/dev/null)
stty $OLDSTTY
INP=$(echo $VAR | od -c | awk '{print $2}')
[ "$INP" = "\\b" ] &&
{
case "$LEN" in
0 ) beep ; continue ;;
1 ) STRING= ;;
* ) STRING="$(echo $STRING | cut -c1-$(($LEN - 1)))" ;;
esac
exec $0 "$STRING"
}
[ "$INP" = "\\r" ] &&
{
echo "\n\nInput number was '$STRING'\n"
exit 0
}
[ $LEN -ge $MAX ] &&
{
beep
continue
}
VAR=$(echo $VAR | tr -cd '[0-9.]')
[ -z "$VAR" ] && beep
done
STRING="$STRING$VAR"
exec $0 $STRING

[Chua Wen Ching]

Thank you Jean Louis Phelix a lot. This script really save me a lot. How do you manage to figure it out the logic?

[Chua Wen Ching]

The code is excellent where i ctrl + c or esc it is still in the input mode. But can you add some comments as i am quite confuse with the script. Comments can help (if any)

1) What if i want to enter alphanumeric how do i validate in your script?
2) If there is more than 2 inputs:
Enter number : [0000] (4 numbers)
Enter name : [aaaaaaaaaaa] (11 alphabets)
Do i need to do validations for both the inputs or ?
3) If there is more than 10 inputs using this method, will it increase the unix uptime?
4) Which line of code disable the usage of crtl + c, ctrl + d, etc?

Thank you Jean Louis Phelix.