I have two variables such as:
path='data\voc11\SegmentationClassExt\%s.png'
name='123'
I want to concatenate two strings into one like so:
data\voc11\SegmentationClassExt\123.png
I used the code below:
sprintf(path, name)
However I receive the following error:
Warning: Control Character '\S' is not valid. See 'doc sprintf' for control characters valid in the format string.
ans =
dataoc11
I am using MATLAB on Windows. Could you give me any solution for that. I tried to change path='data\\voc11\\SegmentationClassExt\\%s.png' and when I did that, the above code will work. However, the current data is
path='data\voc11\SegmentationClassExt\%s.png';
use the matlab function fullfile
filename = fullfile ( path, [name '.png'] );
or
filename = fullfile ( path, sprintf ( '%s.png', name ) );
Note: you should avoid using path as a variable as it is already a Matlab function
Before we start, it's highly advised that you do not use path as a local variable. path is a global variable that MATLAB uses to resolve function scope, especially if you are going to use any functions from toolboxes. Overwriting path with your own string will actually make MATLAB not function properly. Use a different variable name.
Now to resolve your problem, you can use either fullfile as what #matlabgui has suggested, or if you don't care about OS compatibility and are only working in Windows, you can either manually change the path as you have placed so that you can introduce two back slashes and it will indeed work on Windows OS, or you can perhaps use a string replace function so that all back slashes will be accompanied with an additional back slash.
Either one of these two methods will work:
Method 1 - Using regular expressions
pat = 'data\voc11\SegmentationClassExt\%s.png';
pat_new = regexprep(pat, '\\', '\\\\');
The function regexprep performs a string replacement by regular expressions. We search for all single backslashes and replace them with double backslashes. Note that the single back slash \ is a special character in regular expressions so if you explicitly what to look for back slashes, you must place an additional back slash beside it.
Method 2 - Using strrep
pat = 'data\voc11\SegmentationClassExt\%s.png';
pat_new = strrep(pat, '\', '\\');
strrep stands for String Replace. It works very similar to regular expressions as we have discussed above. However, what's nice is that you don't have to append an additional back slash when looking for the actual character.
Once you do this, you can use sprintf as normal:
pat_new = sprintf(pat_new, name);
Related
I have the following sample string:
'-Dparam="x" -f hello-world.txt bye1.txt foo_bar.txt -Dparam2="y"'
I am trying to use RegEx (PowerShell, .NET flavor) to extract the filenames hello-world.txt, bye1.txt, and foo_bar.txt.
The real use case could have any number of -D parameters, and the -f <filenames> argument could appear in any position between these other parameters. I can't easily use something like split to extract it as the delimiter positioning could change, so I thought RegEx might be a good proposition here.
My attempt is something like this in PowerShell (can be opened on any Windows system and copy pasted into it):
'-Dparam="x" -f hello-world.txt bye1.txt foo_bar.txt -Dparam2="y"' -replace '^.* -f ([a-zA-Z0-9_.\s-]+).*$','$1'
Desired output:
hello-world.txt bye1.txt foo_bar.txt
My problem is that I either only take hello-world.txt, or I get hello-world.txt all the way to the end of the string or next = symbol (as in the example above).
I am having trouble expressing that \s is allowed, since I need to capture multiple space-delimited filenames, but that the combination of \s-[a-zA-Z] is not allowed, as that indicates the start of the next argument.
I recently discovered that you can get powershell's functions by reference using the modifier $function:. But I noticed a strange problem...
By convention, POSH uses a {Verb}-{Noun} convention for function names, where {Verb} is part of aproved POSH verb names. For instance: Get-Member or Invoke-WebRequest.
The thing is, that calling $function:Get-Member, for example, is not valid because of the hyphen; it works just fine if you declare a function like ShowMessage and calls: $fn = $function:ShowMessage. So I'd like to know if there's a way to escape this call.
PS.: I do know of another option, but is much much more verbose:
function Show-Message { Write-Host "Foo"; }
$fn = (Get-Item "function:Show-Message").ScriptBlock;
$fn.Invoke();
Update: Although #PetSerAl was very helpfull and explained the problem, I'll mark #Ansgar Wiechers's response as the answer because it's better documented.
function: is a PSDrive, not a (scope)modifier. As for using it with variable-like notation ($function:name): the rules for variable names with special characters apply here as well.
From the documentation:
VARIABLE NAMES THAT INCLUDE SPECIAL CHARACTERS
Variable names begin with a dollar sign. They can include alphanumeric characters and special characters. The length of the variable name is limited only by available memory.
Whenever possible, variable names should include only alphanumeric characters and the underscore character (_).Variable names that include spaces and other special characters, are difficult to use and should be avoided.
To create or display a variable name that includes spaces or special characters, enclose the variable name in braces. This directs PowerShell to interpret the characters in the variable name literally.
Your notation should thus look like this:
${function:Show-Message}
It can be invoked like this:
& ${function:Show-Message}
dir1 = '/tmp1';
dir2 = '/tmp2'
If we do the following
addpath [dir1 dir2];
MATLAB takes '[dir1 dir2]' as the path name to add. We can do the following
eval(sprintf(...
'addpath %s;', ...
[dir1 dir2]));
I was wondering if there is any better way. Thank you,
A very simple way to achieve what you want is to call:
addpath(fullfile(dir1,dir2));
Fullfile will take care of adjusting the string to be a proper folder name (under both Windows and Unix) as in:
fullfile('foo','bar') % returns foo/bar
fullfile('foo/','bar') % returns foo/bar
To add files recursively just do:
pathsToAdd = genpath(fullfile(dir1,dir2));
addpath(pathsToAdd);
The general issue that you are having is that MATLAB has two ways of calling commands. The first does not use an explicit function call function() but rather just multiple inputs on the command line separated by a space:
addpath directory1 directory2
As you know this will add both directory1 and directory2 to the path.
What is happening here is that MATLAB converts all of the inputs to strings implicitly and passes them to the addpath function. The explicit equivalent is
addpath('directory1', 'directory2')
As you can see, internally MATLAB calls addpath like a normal function with input parameters, and as such you can pass it variables rather than string literals:
dir1 = 'directory1';
dir2 = 'directory2';
addpath(dir1, dir2);
This is why you are seeing an issue with:
addpath [dir1 dir2]
Because, as written, [dir1 dir2] is convert to a string (implicitly) since it was passed using the function parameter1 parameter2 syntax rather than the explicit function syntax.
Also, be careful because [dir1, dir2] doesn't do what you think it does. What it actually does it appends the strings dir1 and dir2 and would result in:
[dir1, dir2]
/tmp1/tmp2
If that is what you expect, then use fullfile rather than basic horizontal concatenation to ensure you have the proper file separators, etc.
addpath(fullfile(dir1, dir2));
You will actually see the implicit syntax in many MATLAB functions that accept only strings as input parameters. It is important to know, though, that you can always use the explicit function call function() instead to pass input strings which may be stored in variables.
I have a script where function parameters are expressed like this:
param(
${param1},
${param2},
${param3}
)
What does it mean? I have been unable to find documentation on this.
What's the point of writing parameters that way instead of the more usual
param(
$param1,
$param2,
$param3
)
?
#MikeZ's answer is quite correct in explaining the example in the question, but as far as addressing the question title, there is actually more to say! The ${} notation actually has two uses; the second one is a hidden gem of PowerShell:
That is, you can use this bracket notation to do file I/O operations if you provide a drive-qualified path, as defined in the MSDN page Provider Paths.
(The above image comes from the Complete Guide to PowerShell Punctuation, a one-page wallchart freely available for download, attached to my recent article at Simple-Talk.com.)
They are both just parameter declarations. The two snippets are equivalent. Either syntax can be used here, however the braced form allows characters that would not otherwise be legal in variable names. From the PowerShell 3.0 language specification:
There are two ways of writing a variable name: A braced variable name, which begins with $, followed by a curly bracket-delimited set of one or more almost-arbitrary characters; and an ordinary variable name, which also begins with $, followed by a set of one or more characters from a more restrictive set than a braced variable name allows. Every ordinary variable name can be expressed using a corresponding braced variable name.
From about_Variables
To create or display a variable name that includes spaces or special characters, enclose the variable name in braces. This directs Windows PowerShell to interpret the characters in the variable name literally.
For example, the following command creates and then displays a variable named "save-items".
C:\PS> ${save-items} = "a", "b", "c"
C:\PS> ${save-items}
a
b
c
They are equivalent. It's just an alternative way of declaring a variable.
If you have characters that are illegal in a normal variable, you'd use the braces (think of it as "escaping" the variablename).
There is one additional usage.
One may have variable names like var1, var2, var11, var12, var101, etc.
Regardless if this is desirable variable naming, it just may be.
Using brackets one can precisely determine what is to be used:
assignment of $var11 may be ambiguous, using ${var1}1 or ${var11} leaves no room for mistakes.
I'm creating a PowerShell script that will assemble an HTTP path from user input. The output has to convert any spaces in the user input to the product specific codes, "%2F".
Here's a sample of the source and the output:
The site URL can be a constant, though a variable would be a better approach for reuse, as used in the program is: /http:%2F%2SPServer/Projects/"
$Company="Company"
$Product="Product"
$Project="The new project"
$SitePath="$SiteUrl/$Company/$Product/$Project"
As output I need:
'/http:%2F%2FSPServer%2FProjects%2FCompany%2FProductF2FThe%2Fnew%2Fproject'
To replace " " with %20 and / with %2F and so on, do the following:
[uri]::EscapeDataString($SitePath)
The solution of #manojlds converts all odd characters in the supplied string.
If you want to do escaping for URLs only, use
[uri]::EscapeUriString($SitePath)
This will leave, e.g., slashes (/) or equal signs (=) as they are.
Example:
# Returns http%3A%2F%2Ftest.com%3Ftest%3Dmy%20value
[uri]::EscapeDataString("http://test.com?test=my value")
# Returns http://test.com?test=my%20value
[uri]::EscapeUriString("http://test.com?test=my value")
For newer operating systems, the command is changed. I had problems with this in Server 2012 R2 and Windows 10.
[System.Net.WebUtility] is what you should use if you get errors that [System.Web.HttpUtility] is not there.
$Escaped = [System.Net.WebUtility]::UrlEncode($SitePath)
The output transformation you need (spaces to %20, forward slashes to %2F) is called URL encoding. It replaces (escapes) characters that have a special meaning when part of a URL with their hex equivalent preceded by a % sign.
You can use .NET framework classes from within Powershell.
[System.Web.HttpUtility]::UrlEncode($SitePath)
Encodes a URL string. These method overloads can be used to encode the entire URL, including query-string values.
http://msdn.microsoft.com/en-us/library/system.web.httputility.urlencode.aspx