Bash script function that changes the value of a variable

Question

I'd like to make a function for a BASH script that changes the value of one of its arguments, that is a variable. The function that I did is:

chck_rgx () { # Checks that the given name for a user/group fulfills the regex. The function's parameters are                                                                                                         
              #   * $1: kind of name to check: username, hostname, etc.
              #   * $2: variable whose value to check if meets the requirements.                         
  local rgx_hostname='^[a-z][a-zA-Z0-9_-]+$' ;                                                                                          
  local rgx_inputbox_hostname="The hostname you just submitted isn't a valid name. Try with another name."
  local rgx_username='^[a-z][a-z0-9_-]+$' ;
  local rgx_inputbox_username="The username you just submitted isn't a valid name. Try with another name." ;
  eval rgx_name="\$rgx_$1" ;                                                                                                            
  eval rgx_inputbox="\$rgx_inputbox_$1" ;                                                                                               
  eval name_ch="\$$2" ;                                                                                                                 
  while [[ ! $name_ch =~ $rgx_name ]] ; do                                                                                              
    dialog --backtitle "$backtitle_var" \       
           --title     "Wrong $1 submitted" --clear \                                                           
           --inputbox  "$rgx_inputbox" 0 0 2> name-ch ;                                                                              
    name_ch=$(cat name-ch) ;                                                                                                            
    rm name-ch ;                                                                                                                        
  done                                                                                                                                  
  chckd_var="$name_ch" ;
}

Then in some part of the script there is a dialog box asking you to insert a name and then this function checks if the given name is a valid name. For instance,

dialog  --backtitle "$backtitle_var" \                                                                                              
        --title     "Submit the username" --clear \                                                                  
        --inputbox  "Which username do you want?" 0 0 2> user-name ;                                             
user_name=$(cat user-name) ;                                                                                                          
chck_rgx username user_name ;                                                                                                 
user_name=$chckd_var ;

The problem I have is that the "output" of my function, the value I have now, is not in the same variable I used in the first place. I have to assign the value of the "output" of my function ($chckd_var) to the variable that I inserted as an argument in the function (user_name). What I want to do is that the function changes the value of the global variable user_name (or whatever other variable).

Also, I'd like to know if there's a way to get the output of a dialog inputbox directly in a variable; not in a file.

I'm fairly new to BASH scripts, so perhaps the answer is quite simple. Anyway, I've been looking for this on the web and haven't found the answer.

I read the title and first paragraph. I can not tell what your objective is. — ctrl-alt-delor, Dec 04 '22 at 10:50

score 0 · Answer 1 · answered Jul 28 '15 at 22:07

Well, I think that I found the answer to my first question by the suggestions I had when writing the title for my question in Stack Exchange. I think it works know with just a change:

chck_rgx () { # Checks that the given name for a user/group fulfills the regex. The function's parameters are                                                                                                         
              #   * $1: kind of name to check: username, hostname, etc.
              #   * $2: variable whose value to check if meets the requirements.                         
  local rgx_hostname='^[a-z][a-zA-Z0-9_-]+$' ;                                                                                          
  local rgx_inputbox_hostname="The hostname you just submitted isn't a valid name. Try with another name."
  local rgx_username='^[a-z][a-z0-9_-]+$' ;
  local rgx_inputbox_username="The username you just submitted isn't a valid name. Try with another name." ;
  eval rgx_name="\$rgx_$1" ;                                                                                                            
  eval rgx_inputbox="\$rgx_inputbox_$1" ;                                                                                               
  eval name_ch="\$$2" ;                                                                                                                 
  while [[ ! $name_ch =~ $rgx_name ]] ; do                                                                                              
    dialog --backtitle "$backtitle_var" \       
           --title     "Wrong $1 submitted" --clear \                                                           
           --inputbox  "$rgx_inputbox" 0 0 2> name-ch ;                                                                              
    name_ch=$(cat name-ch) ;                                                                                                            
    rm name-ch ;                                                                                                                        
  done                                                                                                                                  
  declare -g -- "$2=$name_ch" ;
}

The change is in

declare -g -- "$2=$name_ch"

Anyway, I still want to know if there is a way to get the output of a dialog inputbox directly in a variable; not in a file.

Thanks.

yaegashi · Answer 2 · 2015-07-30T11:15:09.050

0

You can use the following redirections:

text=$(dialog --backtitle 'foo' --title 'bar' --clear --inputbox 'baz' 0 0 2>&1 >/dev/tty)
case $? in
    0)     echo "Approved with: $text" ;;
    1)     echo "Canceled by the cancel button" ;;
    255|*) echo "Canceled by the escape key" ;;
esac

edited Jul 30 '15 at 11:15

answered Jul 29 '15 at 01:27

yaegashi

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I tried with that and didn't work. It works fine just with 3>&1 1>&2 2>&3 at the end. Thanks. By the way, What's the purpose of |* next to 255? – ctafur Jul 30 '15 at 10:20
Wow, my original code works only on dash or zsh, but doesn't work on bash. On bash I need braces, like `{ text=$(dialog ... 2>&1 >&3); } 3>&1`. Related: http://unix.stackexchange.com/a/65014/116972 – yaegashi Jul 30 '15 at 11:10
I've updated my answer, simplified it to just redirecting stdout to `/dev/tty`. I think it would suffice for `dialog` specific usage. `255|*)` is to designate it's trapping 255 or any other unexpected exit code from `dialog`. You can replace it with `*)`. – yaegashi Jul 30 '15 at 11:24

Bash script function that changes the value of a variable

2 Answers2