simple echo not working in subshell (clearcase)

[Sangal-Arun]

Hi All,

what you will write in a shell script to get rows from "emp" table.

For ex: getsqldata.sh
--
#!/bin/bash

...
...
sqlplus .... << HEREDOC
select * from emp;
...
# more SQL commands....if any
.....
HEREDOC
..
.....
........
# Script ends...

I think the above command will work. when shell scripts encounters sqlplus ....(username/password with appropriate options)...it will execute a subshell and from now onwards till scripts reachs the here document keyword "HEREDOC" as shown above, system will treat each line as a SQL command.

The problem comming here is that: when at $ prompt I enter "cleartool setview jhola-view_user1" it takes me inside a clearcase view called as: "jhola-view_user1" created by user1....a usual nomenclature.

and NOW when inside this view, I can run any clearcase related command to get history/ description about a clearcase file/element...etc...other clearcase commands. That's fine. Means When I entered "cleartool setview jhola-view_user1" command at $ prompt (on my 1st shell/session) system created a subshell. Here I can run any Linux command or Clearcase command. Simple Linux commands like at $ prompt (when Im inside the view) like:

[jhola-view_user1] $ a=10 ; echo $a
10

As you see above that inside my view, when I manually assigned a=10, echo printed its value fine.

BUT, THE BIGGEST issue is coming ....when I want to write a script like below:

getclearcaseviewdata.sh
-----------------------
#!/bin/bash

a=10
echo $a----AKS---printing here
...
....
cleartool setview jhola-view_user1 << HEREDOC
...
....
# clearcase commands
..
...
a=100
echo $a-----SKA----not printing here
...
...
# more clearcase commands.....
.....

HEREDOC
....
.....
...
......
# Script ends...



Kindly let me know, why system printed variable a's value =10 when I manually set that view at command prompt (inside clearcase view, a subshell)....But system didn't prints a's value = 100 as shown in the script above when I'm setting the view in a script and want to print a's value inside here document body.


Any helps will be really appreciated. Pls let me know, if you want more info....but I think, I have explained it more that enough.

Brgds,
/Arun Sangal

[Sangal-Arun]

Any helps will be highly remembered!!!

[Franklin52]

Sorry it's not completely clear to me, but for what I can understand, you can try the export command:

export a=10

Regards

[Sangal-Arun]

Hi Franklin52,

I'm aware of using export command (used to pass variables to child shells).

If I have declared and initialized a variable at either $ prompt (before calling the script or within the script, I'm able to print its value inside the `here document` block. But when I'm assigning a value to a variable inside the block itself, it is not printing that value. (See code at last).

I'm able to print a variable declared at parent shell or within the script, inside the here document ( << ...) block. But when I assigns any variable in the sub-shell itself (created by the command where we have used `here` document funda...system is not printing the value of a variable.

I'm attaching a codebase snippet, that will clear all doubts. Thanks for helping ....but can you find why system is not printing variable a's value =10.

Code:
=========================================
[/a/b/c/aksutil] $ cat ./g
#!/bin/bash
a=100
cleartool setview testkt2_qabuild << EOC
cd /vob/code
a=10
find . -name fmBuild.pl
read;
find . -name fmBuild.pl > ~/aksutil/gg
cat -n ~/aksutil/gg
cleartool shell echo '"$a"'
echo "$a--"
read
EOC

[/a/b/c/aksutil] $ ./g
./Fare/server/fmBuild.pl
1 ./Fare/server/fmBuild.pl
100
100--

[/a/b/c/aksutil] $

I will check later....as I'm done for the day, I know you | Drl will surely help me in this.

(!!!Note: One strange thing, if you run the commands in this scripting at $ prompt 1 by 1, system will print a=10).

Thanks-

[Franklin52]

Try to declare a as a local variable within the here document:

local a=10

Edit:
I don't think it should work, the commands you're given within the here document is interpreted by the program that you invoke (cleartool).
Within the here document, the variable a is an intern variable and it has nothing to do with the "environtment" variable a of the script.

Regards

[drl]

Hi, Sangal-Arun.

I will check later....as I'm done for the day, I know you | Drl will surely help me in this.

I don't know how clearcase may affect this, but the shell will have already done parameter expansion in the EOC-EOC here document. Here's an example of how to protect it, although you may need to adapt it for your purposes. This creates a little procedure on file t1, and executes it, once without protection, once with:

#!/bin/sh

# @(#) s1       Demonstrate here document protection.

echo " sh version: $BASH_VERSION"

echo " Unprotected:"
rm -f t1
a=100
cat > t1 <<EOF
a=10
echo " My value of a is :$a:"
EOF
nl t1
sh t1

echo
echo " Protected:"
rm -f t1
a=200
cat >t1 <<'EOF'
a=20
echo " My value of a is :$a:"
EOF
nl t1
sh t1

exit 0

Producing:

% ./s1
 sh version: 2.05b.0(1)-release
 Unprotected:
     1  a=10
     2  echo " My value of a is :100:"
 My value of a is :100:

 Protected:
     1  a=20
     2  echo " My value of a is :$a:"
 My value of a is :20:

The key to this is to surround the opening string EOF with the quotes, see man bash for details on here documents. Best wishes ... cheers, drl

PS. Please remember to put your scripts, etc., inside CODE tags for easy reading.

[Franklin52]

Excellent explanation drl!

Regards

[Sangal-Arun]

Thanks for saving my life.


Arun