Let's consider the following perl script:
#!/usr/bin/perl
system("C:/Program Files (x86)/Microsoft Visual Studio/2017/Enterprise/Common7/Tools/VsDevCmd.bat");
system("msbuild");
The batch file invoked with the first system call is supposed to set up some environment variables so that the msbuild executable in the second system call can be found.
When I run this perl script I get the following error:
'msbuild' is not recognized as an internal or external command,
operable program or batch file.
So it looks like the environment variables set in the batch file are not made available to the context of the perl script. What can I do to make this work?
Note 1
Running first the batch file from a console window and then running msbuild works fine. So the batch file works as expected and msbuild is actually available.
Note 2
My real-world perl script is much longer. This example here is a massive simplification which allows to reproduce the problem. So I cannot easily replace the perl script with a batch file, for example.
Note 3
The funny thing is: I've been using this perl script for one or two years without any problems. Then suddenly it stopped working.
Your process has an associated environment which contains things like the search path.
When a sub-process starts, the new process has a new, separate, environment which starts as a copy of the parent process's environment.
Any process (including sub-processes) can change their own environment. They cannot, however, change their parent's process's environment.
Running system() creates a new environment.
So when you call system() to set up your environment, it starts a new sub-process with a new environment. Your batch program then changes this new environment. But then the sub-process exits and its environment ceases to exist - taking all of the changes with it.
You need to run the batch file in a parent process, before running your Perl program.
Related
There is a script.sh file
set FABRIC_CFG_PATH=<some path>
set CORE_PEER_LOCALMSPID=<some id>
If I'm running this script in windows, the env variables are not getting set.
Whereas if setting the env using the cmd approach,
E.g., on windows cmd
set FABRIC_CFG_PATH=<some path>
It works fine.
So how can I set the env in windows through a shell script file?
Since your intent is to define current-process-only environment variables (rather than persistently defined ones, which on Windows are stored in the registry) you need to use a script file / batch file that runs in-process in order for environment variables defined therein to be seen by the script's caller.
Therefore:
If the caller is a cmd.exe session, you must use a batch file: a plain-text file with filename extension .cmd (or, less preferably, .bat[1]) that uses cmd.exe syntax.
If the caller is a PowerShell session, you must use a PowerShell script: a plain-text file with filename extension .ps1 that uses PowerShell syntax.
Note: While you can call a .cmd file (batch file) from PowerShell too (but not directly vice versa), this will not work as intended, because of necessity it runs in a (cmd.exe) child process, whose environment variables aren't seen by the PowerShell caller.
As for .sh files: they have no predefined meaning on Windows, but may be defined by third-party applications, such as Git Bash. In the case of the latter, invoking a .sh file passes it to the POSIX-compatible Bash shell, which has its own syntax. More importantly, invoking such a file won't work as intended when called from either cmd.exe or PowerShell, because Bash must run in a child process, and child processes cannot set environment variables for their parents.
cmd.exe / batch-file example:
Create a file named envVars.cmd, for instance, and place the following lines in it:
#echo off
:: Note: Do NOT use `setlocal` here
set "FABRIC_CFG_PATH=C:\path\to\some directory\config"
set "CORE_PEER_LOCALMSPID=42"
Then, from your cmd.exe session / another batch file, call the file as follows to make the environment variable-definitions take effect for the current process (assuming the file is in the current directory):
.\envVars.cmd
You will then able to refer to the newly defined variables as %FABRIC_CFG_PATH% and %CORE_PEER_LOCALMSPID%.
PowerShell example:
Create a file named envVars.ps1, for instance, and place the following lines in it:
$env:FABRIC_CFG_PATH='C:\path\to\some directory\config'
$env:CORE_PEER_LOCALMSPID=42
Then, from a PowerShell session / another PowerShell script, call the file as follows to make the environment variable-definitions take effect for the current process (assuming the file is in the current directory):
./envVars.ps1
You will then able to refer to the newly defined variables as $env:FABRIC_CFG_PATH and $env:CORE_PEER_LOCALMSPID.
[1] See this answer.
After some study on the executables/batch files in windows, I have come to the conclusion that I need to write a batch .bat file to use the set command to set the env variables as I desire.
I need to source configuration file 'eg.conf' to terminal though perl script. I am using system command but its not working.
system('. /etc/eg.conf')
Basically I am writing script in which later point it will use the environment variable (under conf file) for execute other process.
It is not clear what you are trying to achieve, but if you want to make the config available from within Perl AND your config file is valid Perl code you can use do or require (see perldoc for more information).
What you are doing in your code is to spawn a shell with system, include the config inside this shell (which must be in shell syntax) and then exit the shell again which of course throws all the config away on close. I guess this is not what you intend to do, but your real intention is not clear.
What is your goal? Do you need to source eg.conf to set up further calculations from within a perl controlled shell, or are you trying to affect the parent shell that is running the perl script?
Your example call to system('. /etc/eg.conf') creates a new shell subprocess. /etc/eg.conf is sourced into that shell at which point the shell exits. Nothing is changed within the perl script nor in the parent process that spawned the perl script.
One can not modify the environment of a parent process from a child process, without the assistance of the parent process[1]. One generally returns code for the parent shell to source or to eval.
1: ok, one could theoretically affect the parent process by directly poking into its memory space. Don't do that.
I need to abort a Perl script which is running in the background from another script.
Many perl scripts run on our machine. I need to abort one of the them on request. All I will know is the name of the perl script to abort. I need to abort that one particular script without affecting other processes.
I tried killing it using PID/Image Name but it did not work for the below reasons,
1)I do not know the PID of the script (as it runs from a trigger)
2)The script runs in the background, so the image name is always perl.exe and hence if image name is used , it kills all the other perl tasks as well.
I tried to get the perl script name from the 'windows title' and hence the corresponding PID, but it always shows 'NA'.
I even tried to delete the perl script(as I know the name and location) but it also did not work, as it runs the entire script from the memory (even though it is deleted)
Please help me with some options to kill the running perl, from another script.
Your script may write its pid to special file for another script to use.
I have a startup task for my webrole that download some executable file from a blob and then proceed to the installation.
From a .cmd file, I start a power shell script that download the files, then I start the file from the .cmd.
The script works fine if I run it manually through RDP after the publishing is done.
But, when running as startup script, it sometimes (often) fail at different points.
The taskType is set to background.
Last time, the error was that the command PowerShell does not exists...
Also, I use powershell -command set-executionpolicy unrestricted before running my PS script, but I read here that other task may reset this setting and make mine fail.
Quite a mess.
So that makes me think that if I could wait for all other task to perform before starting mine, it would eliminate these kinds of problems
I suppose I could check if some process is running and wait for it to finish, but I have no clue wich process to check.
Or maybe there's another solution.
~edit~
I read here that the error about powershell not existing may be caused by the batch file being saved as UTF-8 in visual studio. I re-writed it from scratch in notepad++ and made sure it is save as ANSI. Then, same error. The full message is :
'PowerShell' is not recognized as an internal or external command,
operable program or batch file.
Again, the script run perfectly from command line in remote desktop.
It would be possible to set an environment variable at the end of the script that is required to finish, then in the script which is awaiting the dependencies, loop until the environment variable is set, then kick off its activities.
You could also run everything from a single powershell script and use the '-asjob' switch on your installer statement, use the 'wait-job' cmdlet to block until the task is complete then carry on. Powershell also offers a '?!' operator which ensures the last statement executed properly.
This might be caused by an encoding issue. As mentioned in this answer you should save your file in ASCII to ensure correct interpretation of your script.
From the linked answer:
Open your whatever.cmd file with your VS 2012 Ultimate. Click on File->Save whatever.cmd as -> on the dialog there is little arrow next to the [save] button. It will show up a menu that will have the option Save with Encoding.
Select it. Now choose "US-ASCII Codepage 20127" from the list of available encodings.
In vbscript, how do I run a batch file or command, in the current cmd prompt window,
without starting a new process.
For example. According to script56.chm (the vbscript help apparently)
Windows Script Host
Run Method (Windows Script Host)
"Runs a program in a new process"
So if I have code that uses that e.g. a VBS file, and a BAT file.
An environment variable g has the value abc g=abc
from that command window,
The VBS file calls the BAT file with windows scripting host Run.
The bat process sets g=z. and finishes.. and the vbs process finishes.
The environment variable is left untouched as g=abc.
I know
CreateObject("Wscript.Shell").Run "c:\test.bat", 0
starts a new window as is clear when using 1 instead of 0. (since 0 hides the window)
How do I
-run the bat file from the vbs, in the same cmd environment that the vbs was called in, so changes affect the cmd environment it was called in?
-In the two windows case which this one is at the moment, how do I access the environment of the parent cmd window, from the batch file?
how do I run a batch file or command, in the current cmd prompt window, without starting a new process?
I don't think you can; your vbscript runs under a script host engine (such as cscript.exe or wscript.exe), and batch files are interpreted by the command interpreter (typically cmd.exe). Both are separate executables and neither is, to my knowledge, available as an in-process library, so you cannot interpret .vbs and .cmd files within the same process. I also highly doubt that the script host engine that is running your VBScript also could run the batch file in its parent cmd.exe - I don't think you can 'inject' a new batch file into a running cmd.exe.
how do I access the environment of the parent cmd window, from the batch file?
Not just access, but change - MSDN's "Changing Environment Variables" is quite explicit on this: "Altering the environment variables of a child process during process creation is the only way one process can directly change the environment variables of another process. A process can never directly change the environment variables of another process that is not a child of that process." You are trying to change the environment of the parent, not child, process. (I do wonder what 'directly' means in the context of this quote, though).
I would guess that the reason for this is security; imagine the havoc that could be wreaked if arbitrary processes could (maliciously or accidentally) change the PATH (or COMSPEC) environment variable of a running process, such as your vbscript host engine process - it could fail to launch your bat file entirely, breaking your program.
It would seem that you're out of luck - however, there are lots of other mechanisms for passing information between processes. Here are a couple of suggestions that are fairly simple to implement when talking between a batch file & vbscript, although it's by no means exhaustive:
Exit codes
Writing to & Parsing the consoleoutput (stdout) or a temp file
If you absolutely need to set environment variables in the parent cmd.exe (and also absolutely need the intermediate step of a vbscript), then you may have to write a wrapper batch file which runs the vbscript, consumes information produced by it and then sets environment variables; because the wrapper cmd is executing in the top-level cmd process, it will be able to change the env vars there.
Footnote: Note that you can change the permanent system/user environment variables (as opposed to process environment variables) from within a VBScript, but I wouldn't recommend this if you are trying to create a transient state; besides this won't affect already-running processes (like the parent cmd.exe) anyway.