This question seems to be rather simple, but even after searching the web for a couple of hours, I was not able to find a solution...
I have a batch file test.bat
set MY_VARIABLE=%~1
echo %MY_VARIABLE%
The point is that I want to call this programm with a semicolon as input parameter, i.e.,
.\test.bat ";",
from both cmd and Windows PowerShell. While this works fine from cmd, PowerShell does not seem to get anything as an input. Is there any way to make this work for both simultaneously?
This is because of command line syntax. The semicolon is one of multiple delimiters, that split the command line into words: a;b would be interpreted as two separate arguments a (%1) and b (%2).
Therefore, quotes are required. Since Powershell uses quotes for string literals (Powershell does its own re-quoting behind the scenes when passing arguments), you need to include them in the string:
.\test.bat '";"'
# or
.\test.bat "`";`""
Or as #mklement0 pointed out, the stop-parsing symbol --% would also be an option:
.\test.bat --% ";"
Note that this is specific to Powershell syntax.
In CMD, this will suffice:
test.bat ";"
Related
I know that both are used in PowerShell but for different contexts.
On the internet there is a paucity of information on this topic and the only site that talks about it (without making me understand the concept) is:
https://www.rlmueller.net/PowerShellEscape.htm
I am a beginner with PowerShell, I am recently approaching it.
A use case of the \ escape came up in the answer to this other topic of mine:
PowerShell removes multiple consecutive whitespaces when I pass arguments to a nested Start-Process command
Is there anyone who can explain to me in detail the difference between the escape backtick ` and backslash \ in PowerShell, with examples and use cases?
At least one source is welcome, but it is not mandatory.
vonPryz's helpful answer covers the PowerShell-internal angle well; let me attempt a systematic summary that includes the PowerShell CLI angle, as well as passing arguments with embedded " to external programs:
Inside a PowerShell session, the only escape character is ` (the so-called backtick), in the following contexts:
Inside an expandable string ("...", double quoted), but not inside a verbatim string ('...', single-quoted); for the supported escape sequences, see the conceptual about_Special_Characters help topic:
# " must be escaped; escape sequence `n expands to a newline.
"3`" of`nrain"
In unquoted command arguments:
# > must be escaped to write verbatim 'a>b',
# since outside a quoted string an unescaped > is a redirection.
Write-Output a`>b
For line-continuations:
# Spread the Get-Date call across two lines.
# Important: ` must be the *very last char* on the line.
Get-Date `
-Year 2525
Note: Various subsystems, whether PowerShell-specific or not, may have their own escaping rules, such as \ in regular expressions and ` in wildcard expressions. Since arguments to those subsystems are delivered via PowerShell strings, it's best to use verbatim string literals, so as to avoid confusion between PowerShell's own string interpolation and what the target subsystem ends up seeing; e.g. 'A $50 fine.' -match '\$50' (\ is needed to treat regex metacharacter $ literally).
When PowerShell is called from the outside, via its CLI, different rules apply, possibly in addition:
In order to adhere to widely used convention for CLIs (command-line interfaces, programs that accept arguments via a command line) on Windows:
In calls to powershell.exe, the Windows PowerShell CLI, " characters must be escaped with a backslash - i.e. as \" - in order to be preserved during parsing of the original command line.
pwsh.exe, the CLI of the cross-platform, install-on-demand PowerShell (Core) 7+ edition, now commendably alternatively accepts ""[1] in lieu of \", which makes calls from cmd.exe more robust. To get the same robustness in Windows PowerShell - from cmd.exe only - use "^"" (sic).
Note that - unlike \" - these escape sequences only work inside an (unescaped) "..." string (e.g., pwsh.exe -c " ""you & I"" " or powershell.exe -c " "^""you & I"^"" "
By contrast, unescaped " have syntactic function on the command line and tell PowerShell where the boundaries between arguments are; these " instances are removed during command-line parsing.
This ensures that outside callers that merely want to invoke a PowerShell script file (.ps1) with arguments, using the -File parameter, can use the conventional syntax and needn't special-case calls to PowerShell's CLI.
However, if you pass a string containing PowerShell code to the CLI, using the -Command parameter, what PowerShell ends up interpreting obviously must be syntactically valid PowerShell code.
Caveat: If you specify neither -Command nor -File:
powershell.exe defaults to -Command
pwsh.exe now defaults to -File
For the differences between -File and -Command calls and when to use which, see this answer.
If you use -Command, there are two, sequential parsing stages:
The command-line parsing stage, where syntactic (unescaped) " are removed, and escaped \" (or "") turn into literal ".
The result of this stage is then parsed as PowerShell code, as it would be from inside a PowerShell session.
Therefore, you may situationally have to combine \ and `-escaping; e.g. (call from cmd.exe):
C:>powershell.exe -Command " \"3`\" of snow as of $(Get-Date)\" "
3" of snow as of 11/04/2021 14:13:41
Note the use of `\" in order to make PowerShell see `", i.e. a properly escaped " inside a "..." string, after command-line parsing.
Alternatively, depending on the specifics of the command(s) you pass to -Command, using embedded '...' quoting may be an option, which simplifies matters, because ' chars. don't require escaping:
C:>powershell.exe -Command " '3\" of snow as of today.' "
3" of snow as of today.
Given that '...' strings in PowerShell are verbatim strings, use of '...' is only an option if you don't require string interpolation (such as the $(Get-Date) subexpression in the prior example).
Escaping " when calling external programs from PowerShell:
As a shell, it is PowerShell's job to pass the arguments that were passed based on its syntax rules to a target executable, so that the verbatim values that result from PowerShell's parsing are passed in a way that makes the target executable see them as such. In other words: PowerShell should perform any required escaping automatically, behind the scenes. (Unlike cmd.exe, PowerShell cannot just pass its own argument syntax through as-is, because external CLIs cannot be expected to understand '...' strings (single-quoting) or `-escaping).
To use a simply example: Passing '3" of snow' should be passed as "3\" of snow" behind the scenes, based on the most widely used escaping convention.
Sadly, up to PowerShell 7.2.x, this is not the case, and embedded " characters in arguments for external programs must additionally, manually be \-escaped in order to be passed through properly.
This has been fixed in PowerShell 7.3, with selective exceptions on Windows - see the new $PSNativeCommandArgumentPassing preference variable
# Broken behavior up to PS v7.2.x
PS> cmd /c echo '{ "foo": "bar" }'
"{ "foo": "bar" }" # !! Embedded " aren't escaped.
PS> choice.exe /d Y /t 0 /m '{ "foo": "bar" }'
{ foo: bar } [Y,N]?Y # !! When parsed by an executable,
# !! embedded " are effectively LOST.
# Manual escaping required.
PS> choice.exe /d Y /t 0 /m '{ \"foo\": \"bar\" }'
{ "foo": "bar" } [Y,N]?Y # OK
This bug has existed since v1, and has never been fixed so as to avoid breaking existing workarounds.
[1] Inside PowerShell, in "..." strings only, you may also use "" to escape an embedded ", as an alternative to `"
The backtick ` is used as the escape character in Powershell. That is, escaping quotes, tabs and whatnot. Unlike in many other environments, Powershell's newline is `n, not \n. This has the benefit of simplifying paths, since those use backslash in Windows.
As for a practical example, in many programming languages one needs to escape the backslashes in paths. If you have an application located at
c:\program files\newApplication\myApp.exe
Its path must be written as
c:\\program files\\newApplication\\myApp.exe
The double-backslash notation means that there is actaully a backslash, not a metacharacter such as tab or newline. Note that the path contains \newApplication. Now, \n usually means a newline, but it clearly isn't the case. The file does not reside in
c:\program files\
ewApplication\myApp.exe
after all, doesn't it?
The escaping is not needed in Powershell, as the backslash doesn't have special meaning by itself. When Powershell sees c:\program files\newApplication\myApp.exe, it doesn't assign any special meaning to the forementioned \n part, it is just a string literal.
The backslash \ is used as the escape character in regular expressions and to signify metacharacters. That is, to match a literal * in regex, it must be escaped, lest it means the Kleene star (zero or more matches).
I want the $mydate variable or the command Get-Date -Format yyyy-MM-dd to expand in the following command line (note the curly braces required by the svn.exe client:
$mydate = Get-Date -Format yyyy-MM-dd
svn log https://svn.apache.org/repos/asf/ -r {Get-Date -Format yyyy-MM-dd}
svn log https://svn.apache.org/repos/asf/ -r {$mydate}
In both cases I am getting the following error:
svn: E205000: Syntax error in revision argument '-encodedCommand'
Why does the variable becomes -encodedCommand? Should I escape curly braces? How? Tick '`' does not work:
Error formatting a string: Input string was not in a correct format..
At line:1 char:1
+ svn log https://svn.apache.org/repos/asf/ -r `{$mydate`}
What am I doing wrong?
I don't have enough points to comment, but try:
svn log https://svn.apache.org/repos/asf/ -r "{$($mydate)}"
The outer " quotes convert it all into a string, so ignores the curly braces. The $() allows the variable to be correctly interpreted (not as a string).
To complement yaquaholic's helpful answer with background information:
Unquoted use of {...} has special meaning in PowerShell: it creates a script block (type [scriptblock]), which is a reusable piece of PowerShell code that can be passed as an argument or stored in a variable for later execution on demand.
Therefore, to pass arguments with embedded { or } characters, quote them (with '...' (literal string, e.g., '{foo}') or "..." (expandable string, e.g. "{$foo}"), as needed).
The behavior that PowerShell exhibits as of Windows PowerShell v5.1 / PowerShell Core 7.0 with unquoted {...} is a known problem:
A script block has no meaning outside of PowerShell, such as when passing arguments to an external program like svn.
By contrast, calling PowerShell's own CLI - powershell.exe (Windows PowerShell), pwsh (PowerShell Core) - with a script block is supported, via behind-the-scenes Base64-encoding of the script block's content, with the encoded string passed via -encodedCommand, and CLIXML serialization applied to arguments and pipeline input - see this comment on GitHub
This mechanism is currently - pointlessly - applied to other external programs too, which is why you saw an -encodedCommand argument appear.
I know there are lots of posts regarding this, but nothing worked for me.
I am trying to run this command line in PowerShell:
C:/Program Files (x86)/ClamWin/bin/clamd.exe --install
I have this in PowerShell:
&"C:/Program Files (x86)/ClamWin/bin/clamd.exe --install"
But all this does is execute clamd.exe, ignoring the --install parameter
How can I get the full command line to run?
Josef Z's comment on the question provides the solution:
& "C:/Program Files (x86)/ClamWin/bin/clamd.exe" --install # double-quoted exe path
or, given that the executable path is a literal (contains no variable references or subexpressions), using a verbatim (single-quoted) string ('...'):
& 'C:/Program Files (x86)/ClamWin/bin/clamd.exe' --install # single-quoted exe path
As for why your own solution attempt failed: The call operator, &, expects only a command name/path as an argument, not a full command line.
Invoke-Expression accepts an entire command line, but that complicates things further and can be a security risk.
As for why this is the solution:
The need for quoting stands to reason: you need to tell PowerShell that C:/Program Files (x86)/ClamWin/bin/clamd.exe is a single token (path), despite containing embedded spaces.
&, the so-called call operator, is needed, because PowerShell has two fundamental parsing modes:
argument mode, which works like a traditional shell, where the first token is a command name, with subsequent tokens representing the arguments, which only require quoting if they contain shell metacharacters (chars. with special meaning to PowerShell, such as spaces to separate tokens);
that is why --install need not, but can be quoted (PowerShell will simply remove the quotes for you before passing the argument to the target executable.)
expression mode, which works like expressions in programming languages.
PowerShell decides based on a statement's first token what parsing mode to apply:
If the first token is a quoted string - which we need here due to the embedded spaces in the executable path - or a variable reference (e.g., $var ...), PowerShell parses in expression mode by default.
A quoted string or a variable reference as an expression would simply output the string / variable value.
However, given that we want to execute the executable whose path is stored in a quoted string, we need to force argument mode, which is what the & operator ensures.
Generally, it's important to understand that PowerShell performs nontrivial pre-processing of the command line before the target executable is invoked, so what the command line looks like in PowerShell code is generally not directly what the target executable sees.
If you reference a PowerShell variable on the command line and that variable contains embedded spaces, PowerShell will implicitly enclose the variable's value in double quotes before passing it on - this is discussed in this answer to the linked question.
PowerShell's metacharacters differ from that of cmd.exe and are more numerous (notably, , has special meaning in PowerShell (array constructor), but not cmd.exe - see this answer).
To simplify reuse of existing, cmd.exe-based command lines, PowerShell v3 introduced the special stop-parsing symbol, --%, which turns off PowerShell's normal parsing of the remainder of the command line and only interpolates cmd.exe-style environment-variable references (e.g., %USERNAME%).
I have a script foo.cmd:
echo %1 %2
In PowerShell I run:
foo.cmd "a,b" "c"
Expected output: a,b c
Actual output: a b
Why?
The double quotes are removed after PowerShell parsed the command line and passes it to CMD for execution, so CMD actually sees a statement
foo.cmd a,b c
Since the comma is one of CMD's delimiter characters that statement is equivalent to
foo.cmd a b c
To avoid this behavior you need to ensure that the double quotes are preserved when passing the arguments to CMD. There are several ways to achieve this. For instance, you could put the double quoted arguments in single qoutes:
foo.cmd '"a,b"' "c"
and change the positional parameters in the batch script to %~1, %~2 so that CMD removes the double quotes from the arguments.
If you have PowerShell v3 or newer you can use the "magic parameter" --% to avoid the nested quotes:
foo.cmd --% "a,b" "c"
You still need %~1 and %~2 in the batch script, though.
I want to open a text file in notepad++ in a particular line number. If I do this in cmdline the command should be:
start notepad++ "F:\Path\test.txt" -n100
And it is working fine from command line. Now I have to do this from tcl. But I can't make this command work with exec. When I try to execute this:
exec "start notepad++ \"F:\Path\test.txt\" -n100"
I am getting this error:
couldn't execute "start notepad++ "F:\Path\test.txt" -n100": no such file or directory.
What am I missing. Please guide.
Similar to this question:
exec {*}[auto_execok start] notepad++ F:/Path/test.txt -n10
First, you need to supply each argument of the command as separate values, instead of a single string/list. Next, to mimic the start command, you would need to use {*}[auto_execok start].
I also used forward slashes instead of backslashes, since you would get a first level substitution and get F:Path est.txt.
EDIT: It escaped me that you could keep the backslashes if you used braces to prevent substitution:
exec {*}[auto_execok start] notepad++ {F:\Path\test.txt} -n10
You can simply surround the entire exec statement in curly braces. Like this:
catch {exec start notepad++.exe f:\Path\test.txt -n10}
I haven't found a perfect solution to this yet. All my execs seem to be different from each other. On windows there are various issues.
Preserving double quotes around filename (or other) arguments.
e.g. in tasklist /fi "pid eq 2060" /nh the quotes are required.
Preserving spaces in filename arguments.
Preserving backslash characters in filename arguments.
[Internally, Windows doesn't care whether pathnames have / or \, but some programs will parse the filename arguments and expect the backslash character].
The following will handle the backslashes and preserve spaces, but will not handle double-quoted arguments. This method is easy to use. You can build up the command line using list and lappend.
set cmd [list notepad]
set fn "C:\\test 1.txt"
lappend cmd $fn
exec {*}$cmd
Using a string variable rather than a list allows preservation of quoted arguments:
set cmd [auto_execok start]
append cmd " notepad"
append cmd " \"C:\\test 1.txt\""
exec {*}$cmd
Note that if you need to supply the full path to the command to be executed, it often needs to be quoted also due to spaces in the pathname:
set cmd "\"C:\\Program Files\\mystuff\\my stuff.exe\" "