Redirecting standard input\output in Windows PowerShell
PowershellPowershell 2.0StdinPowershell Problem Overview
What is the required syntax to redirect standard input/output on Windows PowerShell?
On Unix, we use:
$./program <input.txt >output.txt
How do I execute the same task in PowerShell?
Powershell Solutions
Solution 1 - Powershell
You can't hook a file directly to stdin, but you can still access stdin.
Get-Content input.txt | ./program > output.txt
Solution 2 - Powershell
If there is someone looking for 'Get-Content' alternative for large files (as me) you can use CMD in PowerShell:
cmd.exe /c ".\program < .\input.txt"
Or you can use this PowerShell command:
Start-Process .\program.exe -RedirectStandardInput .\input.txt -NoNewWindow -Wait
It will run the program synchronously in same window. But I was not able to find out how to write result from this command to a variable when I run it in PowerShell script because it always writes data to the console.
EDIT:
To get output from Start-Process you can use option
> -RedirectStandardOutput
for redirecting output to file and then read it from file:
Start-Process ".\program.exe" -RedirectStandardInput ".\input.txt" -RedirectStandardOutput ".\temp.txt" -NoNewWindow -Wait
$Result = Get-Content ".\temp.txt"
Solution 3 - Powershell
For output redirection you can use:
command > filename Redirect command output to a file (overwrite)
command >> filename APPEND into a file
command 2> filename Redirect Errors
Input redirection works in a different way. For example see this Cmdlet http://technet.microsoft.com/en-us/library/ee176843.aspx
Solution 4 - Powershell
Or you can do:
something like:
$proc = Start-Process "my.exe" "exe commandline arguments" -PassThru -wait -NoNewWindow -RedirectStandardError "path to error file" -redirectstandardinput "path to a file from where input comes"
if you want to know if process errored out, add following code:
$exitCode = $proc.get_ExitCode()
if ($exitCode){
$errItem = Get-Item "path to error file"
if ($errItem.length -gt 0){
$errors = Get-Content "path to error file" | Out-String
}
}
I find that this way I do have a better handle on execution of your scripts, when you need to handle external program/process. Otherwise I have encountered situations where script would hang out on some of external process errors.
Solution 5 - Powershell
You can also do this to have standard error and standard out go to the same place:
get-childitem foo 2>&1 >log
Note that ">" is the same as "| out-file", and by default the encoding is unicode or utf 16. Also be careful with ">>", because it can mix ascii and unicode in the same text file. "| add-content" probably works better than ">>". "| set-content" might be preferable to ">".
There's 6 streams now. More info: https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_redirection?view=powershell-5.1
I think all you can do is save to a text file and then read it into a variable after.