Split a NSString to multiple commandline arguments - objective-c

I am getting a commandline string in my application and I am trying to run the same as an NSTask. I can convert it as a C-String and run it using system.
system([commandlineStr cStringUsingEncoding:NSUTF8StringEncoding]);
But I prefer using NSTask instead. For running as NSTask, I need to split the string as command and an array of arguments. Splitting with space doesn't work since there could be arguments with space in between. Currently they are either escaped or quoted. For eg:
cp "~/File with spaces" ~/Folder\ with\ spaces
Is there a built in way to split the string to multiple arguments or write a custom parsing logic for the same.

The format you are trying to parse is the shell command line, there is a program which is rather good at that - the shell. If you did choose to parse it yourself your job would not be finished - you would still have to locate the program to run. The shell does that by taking the command name, cp in your example, and searching for a matching program using a set of paths. To copy this you would have to perform the same search.
There is a much easier way, the shell it itself a program you can invoke with NSTask, and the shell had an option, -c, which takes a single string as argument and parses and execute that string value as a command line. So you can use NSTask, pass the first argument as #"-c", and the second as the string you have. This will handle everything for you - spaces, escapes, pipes, redirection, et al.
HTH

Related

Escape character within single quotes

I'm having an issue figuring out how to ignore signs and variables in a single quote string statement.
I am attempting to update a table with the new text with structure such as:
update xxx
set xxx =
'Our Ref. $BOOKING_NO$
.......
Kind regards'
If your $ chars are being interpreted, it isn't by Oracle ($ isn't special in Oracle anyway, and between single-quotes everything is a string), but rather by your client program or maybe shell script. If, for example, you are running this in SQL*Plus from a Unix-based shell script, you will need to use the appropriate means required by the shell you use to prevent the shell from interpreting $ and ' characters.

Sending an argument to batch file with spaces. VB

I am using a VB to run .bat file and to pass arguments to it.
Right now I managed to run it and to send the arguments to it, but ran into a problem. My arguments might contain spaces inside. I was trying to use quotes, but it didn't seem to work as I expected. So what I am doing:
Running this code: System.Diagnostics.Process.Start("C:\Users\XXXXXXX\Desktop\New.bat", """"+data+"""")
where 'data' is the argument I am sending. For testing it contains the value:
Hel loo
Inside the .bat file I have a code, that opens notepad and writes the argument inside it. With this code I have managed to pass the argument as one with spaces, but the result is:
"Hel loo"
Any ideas how to get rid of the quotes on each side, while still passing the argument as one with spaces?
I cannot escape them or replace with another symbol. This solution needs to pass the argument as one with spaces inside. Is this possible? The program I am working with is not important.
EDIT
This is the content of the .bat file:
set directory_Rexe="C:\Users\XXXXXXX\Desktop\testBat.txt"
set var=%1
echo %var%>%directory_Rexe%
%directory_Rexe%
You have three options here:
Use %~1, which will strip the quotes.
Don't care about putting everything into argument 1 and quoting and use %* instead. You mentioned not wanting that, though.
Don't pass the string as an argument, but as an environment variable instead. This also helps a lot when you have a number of characters in it that need to be escaped.
All options require you to change the batch file, though.
I'd also question the need for a batch file when you have a perfectly capable programming language already at your fingertips. Writing text to a file should actually be easier from VB.

Need clean syntax in batch

Context
I am thinking I can solve a problem with the proper creation of a *.bat file.
I am automating a process in a backup program called Acronis Backup and Recovery.
I am able to make a script (jScript) that creates all the syntax except for one part correctly.
In a normal command prompt the command I would run looks like this
acrocmd backup file --include="C:\documents\Gale_thesis.doc" "D:\Sandbox\!oDC!-IMG_0222.MOV" "C:\temp\magnifyReader" --loc="D:\backups" --arc="Backup1a"
The jScript I am creating can generate this with no problem and save as a *.bat file. This can works perfect if my file names are clean. By clean I mean no characters the batch files think are key words and commands.
Anytime I have a word like “copy” or a character like “!” in a file name it fails.
Question
So I am now wondering if loading variables from a text file would do the trick?
I am sure a lot of readers know that when load multiple file/folder paths at the command line you need to surround them with double quotes.
So I need this variable to have the correct syntax to be parsed by the batch file and work like the example when I type it directly at a command prompt.
I had tried to follow info about using for /f etc.
But the examples are not broad enough for me to understand, nobody seems to explain how to use these variables mixed in with other syntax.
I know a little about working with variable in a *.bat file. My jScript application can produce the text in any format a list, escaped, what ever is needed.
Thanks
I might suggest you to take a look at escaping characters
http://www.robvanderwoude.com/escapechars.php
in for loops !var! is used when delayedexpansion is enabled so you might need to escape it
I used the following code provided by Aacini to test the arguments that are being passed
#echo off
setlocal enabledelayedexpansion
set argCount=0
for %%x in (%*) do (
set /A argCount+=1
set "argVec[!argCount!]=%%~x"
)
echo Number of processed arguments: %argCount%
and since delayedexpansion is enabled I had to escape ! character
arg.bat --include="C:\documents\Gale_thesis.doc" "D:\Sandbox\^^^!oDC^^^!-IMG_0222.MOV" "C:\temp\magnifyReader" --loc="D:\backups" --arc="Backup1a"
Also about the triple escape quotes ^^^
the problem here is that we need to pass two special characters,
1st is the up arrow ^ and 2nd is the exclamation mark !
so the 2nd batch file (the one that reads our arguments) should get ^!
to escape ^ we use ^^ and to escape ! we use ^!
Thanks to Aacini for his code in HERE

Objective-C - How to convert file path to shell conform file path

I want to execute a shell command (I want to touch a file). I use system("shell command") to execute the command.
For example I want to touch the file at path /Users/username/New Folder/. Now I need to convert the NSString in a format that is conform to shell commands like /Users/username/New\ Folder.
Is there any method that does a conversion like this?
NOTE: It is NOT just replacing a whitespace with \. If you have a special character in the path like /Users/username/Folder(foo)/ the "shell path" looks like this /Users/username/Folder\(foo\)/
There is no need to convert the path, you can surround it in single quotes. Just use:
touch 'path'
You can enclose the parameters that contain spaces with " " marks.
touch "/Users/username/New Folder/"
At least this works at the shell prompt
Don't use system. It's insecure and unpredictable. Surrounding the string with quotes is not sufficient.
Use the execve style functions instead. They are simple and secure.

Escaping Double Quotes in Batch Script

How would I go about replacing all of the double quotes in my batch file's parameters with escaped double quotes? This is my current batch file, which expands all of its command line parameters inside the string:
#echo off
call bash --verbose -c "g++-linux-4.1 %*"
It then uses that string to make a call to Cygwin's bash, executing a Linux cross-compiler. Unfortunately, I'm getting parameters like these passed in to my batch file:
"launch-linux-g++.bat" -ftemplate-depth-128 -O3 -finline-functions
-Wno-inline -Wall -DNDEBUG -c
-o "C:\Users\Me\Documents\Testing\SparseLib\bin\Win32\LinuxRelease\hello.o"
"c:\Users\Me\Documents\Testing\SparseLib\SparseLib\hello.cpp"
Where the first quote around the first path passed in is prematurely ending the string being passed to GCC, and passing the rest of the parameters directly to bash (which fails spectacularly.)
I imagine if I can concatenate the parameters into a single string then escape the quotes it should work fine, but I'm having difficulty determining how to do this. Does anyone know?
The escape character in batch scripts is ^. But for double-quoted strings, double up the quotes:
"string with an embedded "" character"
eplawless's own answer simply and effectively solves his specific problem: it replaces all " instances in the entire argument list with \", which is how Bash requires double-quotes inside a double-quoted string to be represented.
To generally answer the question of how to escape double-quotes inside a double-quoted string using cmd.exe, the Windows command-line interpreter (whether on the command line - often still mistakenly called the "DOS prompt" - or in a batch file):See bottom for a look at PowerShell.
tl;dr:
The answer depends on which program you're calling:
You must use "" when passing an argument to a(nother) batch file and you may use "" with applications created with Microsoft's C/C++/.NET compilers (which also accept \"), which on Windows includes Python, Node.js, and PowerShell (Core) 7+'s CLI (pwsh) but not Windows PowerShell's (powershell.exe):
Example: foo.bat "We had 3"" of rain."
The following applies to targeting batch files only:
"" is the only way to get the command interpreter (cmd.exe) to treat the whole double-quoted string as a single argument (though that won't matter if you simply pass all arguments through to another program, with %*)
Sadly, however, not only are the enclosing double-quotes retained (as usual), but so are the doubled escaped ones, so obtaining the intended string is a two-step process; e.g., assuming that the double-quoted string is passed as the 1st argument, %1:
set "str=%~1" removes the enclosing double-quotes; set "str=%str:""="%" then converts the doubled double-quotes to single ones.
Be sure to use the enclosing double-quotes around the assignment parts to prevent unwanted interpretation of the values.
\" is required - as the only option - by many other programs, (e.g., Ruby, Perl, PHP, as well as programs that use the CommandLineToArgv Windows API function to parse their command-line arguments), but it use from cmd.exe is not robust and safe:
\" is what many executables and interpreters either require - including Windows PowerShell - when passed strings from the outside, on the command line - or, in the case of Microsoft's compilers, support as an alternative to "" - ultimately, though, it's up to the target program to parse the argument list.
Example: foo.exe "We had 3\" of rain."
However, use of \" can break calls and at least hypothetically result in unwanted, arbitrary execution of commands and/or input/output redirections:
The following characters present this risk: & | < >
For instance, the following results in unintended execution of the ver command; see further below for an explanation and the next bullet point for a workaround:
foo.exe "3\" of snow" "& ver."
For calling the Windows PowerShell CLI, powershell.exe, \"" and "^"" are robust, but limited alternatives (see section "Calling PowerShell's CLI ..." below).
If you must use \" from cmd.exe, there are only 3 safe approaches from cmd.exe, which are, however quite cumbersome: Tip of the hat to T S for his help.
Using (possibly selective) delayed variable expansion in your batch file, you can store literal \" in a variable and reference that variable inside a "..." string using !var! syntax - see T S's helpful answer.
The above approach, despite being cumbersome, has the advantage that you can apply it methodically and that it works robustly, with any input.
Only with LITERAL strings - ones NOT involving VARIABLES - do you get a similarly methodical approach: categorically ^-escape all cmd.exe metacharacters: " & | < > and - if you also want to suppress variable expansion - %:
foo.exe ^"3\^" of snow^" ^"^& ver.^"
Otherwise, you must formulate your string based on recognizing which portions of the string cmd.exe considers unquoted due to misinterpreting \" as closing delimiters:
in literal portions containing shell metacharacters: ^-escape them; using the example above, it is & that must be ^-escaped:
foo.exe "3\" of snow" "^& ver."
in portions with %...%-style variable references: ensure that cmd.exe considers them part of a "..." string and that that the variable values do not themselves have embedded, unbalanced quotes - which is not even always possible.
Background
Note: This is based on my own experiments. Do let me know if I'm wrong.
POSIX-like shells such as Bash on Unix-like systems tokenize the argument list (string) before passing arguments individually to the target program: among other expansions, they split the argument list into individual words (word splitting) and remove quoting characters from the resulting words (quote removal). The target program is handed an array of individual, verbatim arguments, i.e. with syntactic quotes removed.
By contrast, the Windows command interpreter apparently does not tokenize the argument list and simply passes the single string comprising all arguments - including quoting chars. - to the target program.
However, some preprocessing takes place before the single string is passed to the target program: ^ escape chars. outside of double-quoted strings are removed (they escape the following char.), and variable references (e.g., %USERNAME%) are interpolated first.
Thus, unlike in Unix, it is the target program's responsibility to parse to parse the arguments string and break it down into individual arguments with quotes removed.
Thus, different programs can require differing escaping methods and there's no single escaping mechanism that is guaranteed to work with all programs - https://stackoverflow.com/a/4094897/45375 contains excellent background on the anarchy that is Windows command-line parsing.
In practice, \" is very common, but NOT SAFE from cmd.exe, as mentioned above:
Since cmd.exe itself doesn't recognize \" as an escaped double-quote, it can misconstrue later tokens on the command line as unquoted and potentially interpret them as commands and/or input/output redirections.
In a nutshell: the problem surfaces, if any of the following characters follow an opening or unbalanced \": & | < >; for example:
foo.exe "3\" of snow" "& ver."
cmd.exe sees the following tokens, resulting from misinterpreting \" as a regular double-quote:
"3\"
of
snow" "
rest: & ver.
Since cmd.exe thinks that & ver. is unquoted, it interprets it as & (the command-sequencing operator), followed by the name of a command to execute (ver. - the . is ignored; ver reports cmd.exe's version information).
The overall effect is:
First, foo.exe is invoked with the first 3 tokens only.
Then, command ver is executed.
Even in cases where the accidental command does no harm, your overall command won't work as designed, given that not all arguments are passed to it.
Many compilers / interpreters recognize ONLY \" - e.g., the GNU C/C++ compiler, Perl, Ruby, PHP, as well as programs that use the CommandLineToArgv Windows API function to parse their command-line arguments - and for them there is no simple solution to this problem.
Essentially, you'd have to know in advance which portions of your command line are misinterpreted as unquoted, and selectively ^-escape all instances of & | < > in those portions.
By contrast, use of "" is SAFE, but is regrettably only supported by Microsoft-compiler-based executables and batch files (in the case of batch files, with the quirks discussed above), which notable excludes PowerShell - see next section.
Calling PowerShell's CLI from cmd.exe or POSIX-like shells:
Note: See the bottom section for how quoting is handled inside PowerShell.
When invoked from the outside - e.g., from cmd.exe, whether from the command line or a batch file:
PowerShell [Core] v6+ now properly recognizes "" (in addition to \"), which is both safe to use and whitespace-preserving.
pwsh -c " ""a & c"".length " doesn't break and correctly yields 6
Windows PowerShell (the legacy edition whose latest and final version is 5.1) recognizes only \" or """, the latter being the most robust choice from cmd.exe, in the form "^""" (even though internally PowerShell uses ` as the escape character in double-quoted strings and also accepts "" - see bottom section), as discussed next:
Calling Windows PowerShell from cmd.exe / a batch file:
"" breaks, because it is fundamentally unsupported:
powershell -c " ""ab c"".length " -> error "The string is missing the terminator"
\" and """ work in principle, but aren't safe:
powershell -c " \"ab c\".length " works as intended: it outputs 5 (note the 2 spaces)
But it isn't safe, because cmd.exe metacharacters break the command, unless escaped:
powershell -c " \"a& c\".length " breaks, due to the &, which would have to be escaped as ^&
\"" is safe, but normalizes interior whitespace, which can be undesired:
powershell -c " \""a& c\"".length " outputs 4(!), because the 2 spaces are normalized to 1.
"^"" is the best choice for Windows PowerShell, specifically Credit goes to Venryx for discovering this approach. and "" for PowerShell (Core) 7+:
Windows PowerShell: powershell -c " "^""a& c"^"".length " works: doesn't break - despite & - and outputs 5, i.e., correctly preserved whitespace.
PowerShell Core: pwsh -c """a& c"".length "
See this answer for more information.
On Unix-like platforms (Linux, macOS), when calling PowerShell [Core]'s CLI, pwsh, from a POSIX-like shell such as bash:
You must use \", which, however is both safe and whitespace-preserving:
$ pwsh -c " \"a& c\".length " # OK: 5
# Alternative, with '...' quoting: no escaping of " needed.
$ pwsh -c ' "a& c".length ' # OK: 5
Related information
^ can only be used as the escape character in unquoted strings - inside double-quoted strings, ^ is not special and treated as a literal.
CAVEAT: Use of ^ in parameters passed to the call statement is broken (this applies to both uses of call: invoking another batch file or binary, and calling a subroutine in the same batch file):
^ instances in double-quoted values are inexplicably doubled, altering the value being passed: e.g., if variable %v% contains literal value a^b, call :foo "%v%" assigns "a^^b"(!) to %1 (the first parameter) in subroutine :foo.
Unquoted use of ^ with call is broken altogether in that ^ can no longer be used to escape special characters: e.g., call foo.cmd a^&b quietly breaks (instead of passing literal a&b too foo.cmd, as would be the case without call) - foo.cmd is never even invoked(!), at least on Windows 7.
Escaping a literal % is a special case, unfortunately, which requires distinct syntax depending on whether a string is specified on the command line vs. inside a batch file; see https://stackoverflow.com/a/31420292/45375
The short of it: Inside a batch file, use %%. On the command line, % cannot be escaped, but if you place a ^ at the start, end, or inside a variable name in an unquoted string (e.g., echo %^foo%), you can prevent variable expansion (interpolation); % instances on the command line that are not part of a variable reference are treated as literals (e.g, 100%).
Generally, to safely work with variable values that may contain spaces and special characters:
Assignment: Enclose both the variable name and the value in a single pair of double-quotes; e.g., set "v=a & b" assigns literal value a & b to variable %v% (by contrast, set v="a & b" would make the double-quotes part of the value). Escape literal % instances as %% (works only in batch files - see above).
Reference: Double-quote variable references to make sure their value is not interpolated; e.g., echo "%v%" does not subject the value of %v% to interpolation and prints "a & b" (but note that the double-quotes are invariably printed too). By contrast, echo %v% passes literal a to echo, interprets & as the command-sequencing operator, and therefore tries to execute a command named b.
Also note the above caveat re use of ^ with the call statement.
External programs typically take care of removing enclosing double-quotes around parameters, but, as noted, in batch files you have to do it yourself (e.g., %~1 to remove enclosing double-quotes from the 1st parameter) and, sadly, there is no direct way that I know of to get echo to print a variable value faithfully without the enclosing double-quotes.
Neil offers a for-based workaround that works as long as the value has no embedded double quotes; e.g.:
set "var=^&')|;,%!" for /f "delims=" %%v in ("%var%") do echo %%~v
cmd.exe does not recognize single-quotes as string delimiters ('...') - they are treated as literals and cannot generally be used to delimit strings with embedded whitespace; also, it follows that the tokens abutting the single-quotes and any tokens in between are treated as unquoted by cmd.exe and interpreted accordingly.
However, given that target programs ultimately perform their own argument parsing, some programs such as Ruby do recognize single-quoted strings even on Windows; by contrast, C/C++ executables and Perl do not recognize them.
Even if supported by the target program, however, it is not advisable to use single-quoted strings, given that their contents are not protected from potentially unwanted interpretation by cmd.exe.
Quoting from within PowerShell:
Windows PowerShell is a much more advanced shell than cmd.exe, and it has been a part of Windows for many years now (and PowerShell Core brought the PowerShell experience to macOS and Linux as well).
PowerShell works consistently internally with respect to quoting:
inside double-quoted strings, use `" or "" to escape double-quotes
inside single-quoted strings, use '' to escape single-quotes
This works on the PowerShell command line and when passing parameters to PowerShell scripts or functions from within PowerShell.
(As discussed above, passing an escaped double-quote to PowerShell from the outside requires \" or, more robustly, \"" - nothing else works).
Sadly, when invoking external programs from PowerShell, you're faced with the need to both accommodate PowerShell's own quoting rules and to escape for the target program:
This problematic behavior is also discussed and summarized in this answer; the experimental PSNativeCommandArgumentPassing feature introduced in PowerShell Core 7.2.0-preview.5 - assuming it becomes an official feature - will fix this at least for those external programs that accept \".
Double-quotes inside double-quoted strings:
Consider string "3`" of rain", which PowerShell-internally translates to literal 3" of rain.
If you want to pass this string to an external program, you have to apply the target program's escaping in addition to PowerShell's; say you want to pass the string to a C program, which expects embedded double-quotes to be escaped as \":
foo.exe "3\`" of rain"
Note how both `" - to make PowerShell happy - and the \ - to make the target program happy - must be present.
The same logic applies to invoking a batch file, where "" must be used:
foo.bat "3`"`" of rain"
By contrast, embedding single-quotes in a double-quoted string requires no escaping at all.
Single-quotes inside single-quoted strings do not require extra escaping; consider '2'' of snow', which is PowerShell' representation of 2' of snow.
foo.exe '2'' of snow'
foo.bat '2'' of snow'
PowerShell translates single-quoted strings to double-quoted ones before passing them to the target program.
However, double-quotes inside single-quoted strings, which do not need escaping for PowerShell, do still need to be escaped for the target program:
foo.exe '3\" of rain'
foo.bat '3"" of rain'
PowerShell v3 introduced the magic --% option, called the stop-parsing symbol, which alleviates some of the pain, by passing anything after it uninterpreted to the target program, save for cmd.exe-style environment-variable references (e.g., %USERNAME%), which are expanded; e.g.:
foo.exe --% "3\" of rain" -u %USERNAME%
Note how escaping the embedded " as \" for the target program only (and not also for PowerShell as \`") is sufficient.
However, this approach:
does not allow for escaping % characters in order to avoid environment-variable expansions.
precludes direct use of PowerShell variables and expressions; instead, the command line must be built in a string variable in a first step, and then invoked with Invoke-Expression in a second.
An alternative workaround* that addresses this problem is to call via cmd /c with a single argument containing the entire command line:
cmd /c "foo.exe `"3\`" of rain`" -u $env:USERNAME"
Thus, despite its many advancements, PowerShell has not made escaping easier when calling external programs - on the contrary. It has, however, introduced support for single-quoted strings.
If you don't mind installing a third-party module (authored by me), the Native module (Install-Module Native) offers backward- and forward-compatible helper function ie, which obviates the need for the extra escaping and contains important accommodations for high-profile CLIs on Windows:
# Simply prepend 'ie' to your external-program calls.
ie foo.exe '3" of rain' -u $env:USERNAME
Google eventually came up with the answer. The syntax for string replacement in batch is this:
set v_myvar=replace me
set v_myvar=%v_myvar:ace=icate%
Which produces "replicate me". My script now looks like this:
#echo off
set v_params=%*
set v_params=%v_params:"=\"%
call bash -c "g++-linux-4.1 %v_params%"
Which replaces all instances of " with \", properly escaped for bash.
As an addition to mklement0's excellent answer:
Almost all executables accept \" as an escaped ". Safe usage in cmd however is almost only possible using DELAYEDEXPANSION.
To explicitely send a literal " to some process, assign \" to an environment variable, and then use that variable, whenever you need to pass a quote. Example:
SETLOCAL ENABLEDELAYEDEXPANSION
set q=\"
child "malicious argument!q!&whoami"
Note SETLOCAL ENABLEDELAYEDEXPANSION seems to work only within batch files. To get DELAYEDEXPANSION in an interactive session, start cmd /V:ON.
If your batchfile does't work with DELAYEDEXPANSION, you can enable it temporarily:
::region without DELAYEDEXPANSION
SETLOCAL ENABLEDELAYEDEXPANSION
::region with DELAYEDEXPANSION
set q=\"
echoarg.exe "ab !q! & echo danger"
ENDLOCAL
::region without DELAYEDEXPANSION
If you want to pass dynamic content from a variable that contains quotes that are escaped as "" you can replace "" with \" on expansion:
SETLOCAL ENABLEDELAYEDEXPANSION
foo.exe "danger & bar=region with !dynamic_content:""=\"! & danger"
ENDLOCAL
This replacement is not safe with %...% style expansion!
In case of OP bash -c "g++-linux-4.1 !v_params:"=\"!" is the safe version.
If for some reason even temporarily enabling DELAYEDEXPANSION is not an option, read on:
Using \" from within cmd is a little bit safer if one always needs to escape special characters, instead of just sometimes. (It's less likely to forget a caret, if it's consistent...)
To achieve this, one precedes any quote with a caret (^"), quotes that should reach the child process as literals must additionally be escaped with a backlash (\^"). ALL shell meta characters must be escaped with ^ as well, e.g. & => ^&; | => ^|; > => ^>; etc.
Example:
child ^"malicious argument\^"^&whoami^"
Source: Everyone quotes command line arguments the wrong way, see "A better method of quoting"
To pass dynamic content, one needs to ensure the following:
The part of the command that contains the variable must be considered "quoted" by cmd.exe (This is impossible if the variable can contain quotes - don't write %var:""=\"%). To achieve this, the last " before the variable and the first " after the variable are not ^-escaped. cmd-metacharacters between those two " must not be escaped. Example:
foo.exe ^"danger ^& bar=\"region with %dynamic_content% & danger\"^"
This isn't safe, if %dynamic_content% can contain unmatched quotes.
If the string is already within quotes then use another quote to nullify its action.
echo "Insert tablename(col1) Values('""val1""')"
At Windows 10 21H1.
If from a batch (.bat) file I want to run the Everything application, I use """ inside double quotes argument:
"C:\Program Files\Everything\Everything.exe" -search "<"""D:\My spaced folder""" | """Z:\My_non_spaced_folder"""> <*.jpg | *.jpeg | *.avi | *.mp4>"
Hope it helps.