Bash: How to store a specific line of CLI output into a file?

Question

1. Let's assume I receive the following output after executing a bash script in CLI (so this text will be displayed in terminal):

   POST https://mycompany.com/
   COOKIE='BLABLABLABLABLA'
   HOST='ANYIPADDRESS'
   FINGERPRINT='sha256:BLABLABLABLA'
   

   How can I store the content of COOKIE (only the text between ' and ') into a separate file?

---

2. Furthermore, the mentioned text should be pasted into this external file at a specific position.

   The already existing file content looks like that:

   [global]
   Name = Name of VPN connection
   
   [provider_openconnect]
   Type = OpenConnect
   Name = Name of VPN connection
   Host = IP-address
   Domain = Domain name
   OpenConnect.Cookie = >>>INSERT CONTENT OF THE COOKIE HERE<<<
   OpenConnect.ServerCert = sha256:BLABLABLABLA
   

   How is that possible?

Answer 1

These types of thing are not generic in nature, but specific though approach is generic

---

I am assuming, you want to replace OpenConnect.Cookie = line with OpenConnect.Cookie = BLABLABLABLABLA

So, to first create required string , you can use

sed -i  "s/^OpenConnect.Cookie =.*$/$( command_giving_output  | grep 'COOKIE=' | sed "s/COOKIE='//; s/'//g; s/^/OpenConnect.Cookie = /")/" external_filename

Here I am using command substitution to first create required string

command_giving_output  | grep 'COOKIE=' | sed "s/COOKIE='//; s/'//g; s/^/OpenConnect.Cookie = /"

and then substituting required line by this required string

sed -i  "s/^OpenConnect.Cookie =.*$/output from above command substitution /" external_filename

Answer 2

You could use:

. <(command | grep "^COOKIE=")
sed -i "s/\(OpenConnect.Cookie\)\s*=.*/\1 = ""$COOKIE""/" file

Where:

• file is the existing file with contents as described in the question.
• command is the your command that prints the text to the terminal.
• grep "^COOKIE=" searches for a line starting with COOKIE=
• and the dot in the beginning of the command "sources" the output. This means that the output is interpreted as shell code. Thus the variable $COOKIE is set in the current shell.
• The sed command then replaces the line in the destination file with the contents of the variable $COOKIE.

Answer 3

How about

sed -f <(CLI command | sed -n '/COOKIE=\o047/{s//\/OpenConnect.Cookie =\/ s\/= \.*$\/= /; s/.$/\//p;}') file
[global]
Name = Name of VPN connection

[provider_openconnect]
Type = OpenConnect
Name = Name of VPN connection
Host = IP-address
Domain = Domain name
OpenConnect.Cookie = BLABLABLABLABLA
OpenConnect.ServerCert = sha256:BLABLABLABLA

It creates a "sed script file" on the fly by extracting / massageing the relevant data from your CLI command, and executes this script file using "process substitution" in a second sed call.

Answer 4

You can read the cookie using a combination of bash's read and grep:

IFS="'" read -r _ cookie _ < <(some-command | grep '^COOKIE')

This uses process substitution to feed the output of some-command | grep '^COOKIE') to read. With IFS="='", we split the input on ', discarding the first element of the split (COOKIE=) (and any remaining text after the closing quote), while saving the second in the cookie variable.

Then we can use sed to replace the text:

sed -i 's/>>>INSERT CONTENT OF THE COOKIE HERE<<</'"$cookie"'/' some-file

This depends on the cookie text not containing special characters like &, though.

Answer 5

This answer is based on @MSalters's comment. The shell used is Bash.

prompt% COOKIE=$(./mycmd | grep -Po "(?<=COOKIE=)'[[:alnum:]]+'" | tr -d \')
prompt% echo "$COOKIE" >/tmp/cookie
prompt% sed -i "s:\(OpenConnect.Cookie =\).*:\1 $COOKIE:" file

Alternative solution (using GNU expr)

This solution works if there is only one matching result.

prompt% COOKIE=$(expr "$(./mycmd | grep COOKIE)" : "COOKIE='\([[:alnum:]]\+\)'[[:space:]]*")
prompt% echo "$COOKIE" >/tmp/file
prompt% sed -i "s:\(OpenConnect.Cookie =\).*:\1 $COOKIE:" file