[SOLVED] Control characters in Shell mode (left, right, up and down arrow keys)

jags1984 · 03-27-2013, 06:27 AM

I am writing a console mode shell scipt.I am trying to read a char in my shell script
test.sh

echo "Enter the word"
read ch
echo $ch

Output
-------
[Unix@myunix ~]$ ./test.sh
Enter the word
Hello wonld^[[D^[[D

Issue: Here u see i miss spelled Hello world as Hello wonld.

I am trying to use left arrow keys to go back to the characted 'n' and change it to 'r'. Here the left arrow keys are pressed 2 times. It is displaying ^[[D instead of going back one character.

Can you pls let me know what changes i need to make to work as i expect.

I am using "GNU bash, version 4.2.39(1)-release"

Thanks and Regards,
Jagadish

manu-tm · 03-27-2013, 07:45 AM

echo only displays the string you entered, it doesn't allow you to edit it.

man echo

jags1984 · 03-27-2013, 07:52 AM

I m not echoeing...I m trying to edit the text in read mode...

manu-tm · 03-27-2013, 08:14 AM

Oops, sorry for the confusion. Anyways, 'read' only allows you to add or remove characters in the string to be entered (no real editing capabilities). Left and right arrows are interpreted as combinations of ascii characters. Still, using the backspace key is ok.

http://wiki.bash-hackers.org/commands/builtin/read

shivaa · 03-27-2013, 08:28 AM

In that case, if you have typed something wrong, you should use Unix based keyboard shorcuts like:

Quote:

CTRL+h ......... To remove characters one by one from cursor position
CTRL+u ......... To remove everything that you've typed. It's undo

Quote:

Originally Posted by manu-tm

echo only displays the string you entered, it doesn't allow you to edit it.

man echo

OP has typed what echo command is asking for through read, and that can be erased easily using CTRL+u or CTRL+h.

manu-tm · 03-27-2013, 08:52 AM

(Damn! Yet I know pretty well that I should never ever attempt to answer before my safe caffeine level is reached...)

Kenhelm · 03-27-2013, 10:25 AM

Bash read has a -e option; it uses readline to obtain the line if the shell is interactive. Try

Code:

read -e ch

jags1984 · 03-27-2013, 11:38 PM

Thanks,

read -e ch

works, actually i am developing a console menu using cmmds tput cup I am designing it.

It looks like something like this

1.Name :
2.Address :
3.Phone :

When I trying editing something it crosses my variables and i can reach till Left most part and even I can write words on the screen like Water.

Water 1.Name :Tiger
2.Address :
3.Phone :

I dont want it to cross ':' when in editable mode. It should stop at T of Tiger when left arrow keys are used and should not allow to traverse further.

shivaa · 03-28-2013, 12:35 AM

Let's know what exactly you're doing and what you've done. In the meantime you can try with following, which do not cross ':' and stops when it reaches to ': '

Code:

echo -e "Name: \n"; read name
echo -e "Address: \n"; read addr
echo -e "Phone: \n"; read phone

Please use [code][code] around commands output that you're sharing. This option is available under menu when you Reply to Thread.

Kenhelm · 03-28-2013, 01:00 AM

Try using the -p option to stop the cursor going to the beginning of the line.

Code:

read -ep '1.Name : ' ch

jags1984 · 03-28-2013, 03:44 AM

Thanks

I am desiging a console

And my menu looks something like this

1.Name :
2.Address :
3.Phone :

Tput cup etc commands I am using to design the screen, read -ep works

but i am doing

read -ep ch

where 'ch' would be the input that I would be reading

1.Name :
2.Address :
3.Phone :

It works but i get ch character defaulty

1.Name :ch
2.Address :
3.Phone :

jags1984 · 03-28-2013, 03:54 AM

Also now the backspace and delete takes the cursor to left most row and it overwrites the console .

David the H. · 03-28-2013, 06:06 AM

First of all, please use ***[code][/code]*** tags around your code and data, to preserve the original formatting and to improve readability. Do not use quote tags, bolding, colors, "start/end" lines, or other creative techniques.

Next, no, it's not "read -ep ch". "-p" is the "prompt" option, the text that follows it will appear to the left of the actual typing area. The prompt text will not be saved to the variable, so you'll have to append it later if you need it.

Code:

read -re -p "Please enter your name: ' name
read -re -p "Please enter your address: ' address
read -re -p "Please enter your phone number: ' phone

echo 'Your information:'
echo "Name=$name"
echo "Address=$address"
echo "Phone No=$phone"

There's no way inside the script to control what goes on inside the edit box while it's in use. You can only pre-insert text and/or edit it after you get it.

One thing that most coders do in this situation is put the read inside a perpetual loop, and only break out of it when the reply matches some preset condition.

Code:

while true; do

    read -re -p "Please enter your name: ' name

    case $name in
        *[^[:alnum:]]*) echo "The name must only contain letters or numbers.  Try again." ;;
        *) break  ;;
    esac

done

jags1984 · 03-31-2013, 11:44 PM

I am displaying the Name and all using tput and cup now I only wanna read

Code:

  if [ "$rec_flag" == "N" ]
        then
                while [ "$chk_flag" != "Y" ]
                do
                        tput cup $rec_ind `expr $col_no + 2`
                        read -re -p ch

the code read -re -p ch doesnt store the input in ch instead it displays the the variable ch on screen.

Kenhelm · 04-01-2013, 04:34 AM

Quote:

the code read -re -p ch doesnt store the input in ch instead it displays the the variable ch on screen.

The -p option expects some text after it. The first parameter after -p is seen as text. It is displayed as the read prompt.

Code:

read -re -p ch                # wrong; ch is seen as text
read -re -p "some_text" ch    # correct; ch is now the read variable

Quote:

I am displaying the Name and all using tput and cup now I only wanna read

In that case, continue using tput and cup to display your prompts but without the ' :'
1.Name
2.Address
3.Phone
then put in the ' :' with read -p

Code:

read -re -p " :" ch