Read Bash environment variable in TCL

Question

How to read a shell environment variable in your Tcl script. So anyone please help me. I am very new in TCL.

score 35 · Answer 1 · edited Apr 01 '11 at 16:35

35

Use $::env to access any environment variables e.g. to access the TMP environment variable do this:

set tmpdir $::env(TMP)

More info here http://wiki.tcl.tk/1624

edited Apr 01 '11 at 16:35

Bryan Oakley

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answered Apr 01 '11 at 08:54

TrojanName

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Just i write your code and execute it. But i am not getting. I am in tclsh prompt. My prompt is %. so what i did just type in the prompt % set tmpdir $::env(TMP). The output is like that can't read "::env(TMP)": no such variable – galvin Verghese Apr 01 '11 at 08:58
Actually i want to write a proc is tcl that returns the Bash environment variable values. – galvin Verghese Apr 01 '11 at 09:39
1

That's because you have no environment variable called TMP. Did you read the link I gave you? – TrojanName Apr 01 '11 at 11:17
Ah, I can see the conversation you're having with the other responder - I think you'll be ok! – TrojanName Apr 01 '11 at 11:20

score 5 · Answer 2 · answered Apr 01 '11 at 08:56

5

$ export var=42
$ tclsh
% puts $env(var)
42

answered Apr 01 '11 at 08:56

hynek

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TMP environment variable is define in the bash script. so what i want to do just access the environment variable in the tcl. my tcl prompt is %. so finally i want to access the environment variable in tcl. – galvin Verghese Apr 01 '11 at 09:03
The TMP enviroment variable would be $env(TMP). **But**: Is the tcl script called from the bash script? Is the variable global (ie. export)? – hynek Apr 01 '11 at 09:06
Yea. It is working fine. but my question is that what ever environment variable is defined in bash or shell script just i want to access using the proc in tcl. so please........ – galvin Verghese Apr 01 '11 at 09:08
yea. TMP variable is the environment variable that is defined in bash script. TMP=/tmp ORACLE_SID=DBTEST ORACLE_HOME=/opt/oracle/product/102 export ORACLE_SID ORACLE_HOME so here i want to access the environment variable ORACLE_SID and ORACLE_HOME, so how i should do, please ........ – galvin Verghese Apr 01 '11 at 09:13
So you want a list of _all_ defined shell variables? – hynek Apr 01 '11 at 09:16
See what i am doing here. I am writing my all steps: – galvin Verghese Apr 01 '11 at 09:18
It's all analogous: The bash variable ORACLE_SID can be accessed using $env(ORACLE_SID) in your tcl script. – hynek Apr 01 '11 at 09:20
Please just edit your question with the steps, that will be the easiest. – hynek Apr 01 '11 at 09:21
See what i am doing here. I am writing my all steps: 1. I am using linux 5.0 server. so i am in admin prompt and my prompt is #. My Prompt is [root@db1~] #. 2. after that what i did type tclsh. 3. so now i am in tcl prompt i.e. % (percentage) 4. Type here: su - oracle 5. after that my current working directory is /home/oracle/ and my prompt is $(Dollar). 6. now i again type here tclsh 7. so now i am in % prompt and after that final step 8. puts $env(ORACLE_SID) 7. so here i am getting the exact output DBTEST. so there are the process i am doing here. But what i want i want to write a tcl proc – galvin Verghese Apr 01 '11 at 09:29
so finally i want to write a tcl proc to return the bash environment variable. please help me – galvin Verghese Apr 01 '11 at 09:31
Your problem seems to be the su rather than reading out the variable. You can't just call "su - oracle" inside of a script and read out the bash variables. The easiest way I can suggest is running your tcl script as 'su - oracle -c "tclsh /absolute/path/your-script.tcl"' - you can write a bash wrapper around that of course. – hynek Apr 01 '11 at 09:43

score 3 · Answer 3 · answered Apr 01 '11 at 16:41

3

Environment variables are accessible via the built-in global variable env (fully qualified it is ::env). You use this like any other Tcl array.

If you want to print a list of all environment variables you can use something like this:

proc dump_env_vars {} {
    foreach name [array names ::env] {
        puts "$name == $::env($name)"
    }
}

Of course, to access just a single variable you use it like any other array, for example:

puts "HOME = '$::env(HOME)'"

For more information see the env page on the Tcler's wiki and the env section of the tclvars man page

answered Apr 01 '11 at 16:41

Bryan Oakley

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yea, your procedure is executed, it gives all the environment variables. its ok. But what i am asking here. Suppose in bash script if i define the user define environment like this : ORACLE_SID=DBTEST ORACLE_HOME=/opt/oracle/product/102 export ORACLE_SID ORACLE_HOME Now i want to write a proc in tcl to access the environment variable that is defined by user. so how can i do it. please.......... – galvin Verghese Apr 02 '11 at 05:29
I also read u r link. But it is not match with my requirement. – galvin Verghese Apr 02 '11 at 05:49
I just use `parray env` when I want to dump environment variables. – Donal Fellows Apr 02 '11 at 07:34
Here Actually parray is used for print the env values. But what i want how to access the environment variable in TCL, that is defined in bash script, so please help me...... – galvin Verghese Apr 06 '11 at 06:09

score 2 · Answer 4 · answered Apr 17 '15 at 12:31

To read a shell environment variable in Tcl script, try doing something like this:

global env
set olddisplay $env(DISPLAY)
set env(DISPLAY) unix:0

This might be expressed as well in this fashion:

set olddisplay $::env(DISPLAY)
set ::env(DISPLAY) unix:0

and forget about global.

You can check to see if the variable exists by doing something like:

if {[info exists env(VARNAME)]} {
    # okay, it's there, use it
    set value $env(VARNAME)
} else {
    # the environment var isn't set, use a default
    set value "the default value"
}

This is source.

Read Bash environment variable in TCL

4 Answers4