How to decleare char *const argv[] in swift [duplicate]

Question

I am trying to make a c style array of chars pointer like this:

*const argv[]

I figured out i have to use UnsafePointer<UnsafeMutablePointer<Int8>>

but i don't know how to initialize it.

How can i map this normal Array to UnsafePointer<UnsafeMutablePointer<Int8>> :

let argv = ["/usr/bin/printf", "BBB"]

Thank you

This is invalid *const argv[] , what are you trying to do? — Iharob Al Asimi
– Iharob Al Asimi, Commented Oct 29, 2015 at 1:51
@iharob Run this function ==> public func execvp(_: UnsafePointer<Int8>, _: UnsafePointer<UnsafeMutablePointer<Int8>>) -> Int32 — Omid Yaghoubi
– Omid Yaghoubi, Commented Oct 29, 2015 at 1:54
@iAdjunct This question has nothing to do about argv & argc it's something different. I'm trying to create an array with char pointers. Not duplicate. — Omid Yaghoubi
– Omid Yaghoubi, Commented Oct 29, 2015 at 2:08

matt · Accepted Answer · 2015-10-29 03:18:37Z

3

The easy way is to let Cocoa form the C strings for you:

let args = ["/usr/bin/printf","BBB"]
var cs = UnsafeMutablePointer<UnsafeMutablePointer<Int8>>.alloc(2)
for (ix,s) in args.enumerate() {
    cs[ix] = UnsafeMutablePointer<Int8>((s as NSString).UTF8String)
}
var cs2 : UnsafePointer<UnsafeMutablePointer<Int8>> = UnsafePointer(cs)

Beware; cs does not contain copies. Its pointers are pointing right into the strings in args.

edited Oct 29, 2015 at 3:18

answered Oct 29, 2015 at 2:53

matt

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7 Comments

Omid Yaghoubi Over a year ago

Thank you @matt , but i need UnsafePointer<UnsafeMutablePointer<Int8>> not a UnsafeMutablePointer<UnsafePointer<Int8>> . UnsafePointer doesn't have alloc , UnsafeMutablePointer has. can you explain me how to make a UnsafePointer<UnsafeMutablePointer<Int8>> with this method ?

matt Over a year ago

let cs2 : UnsafePointer<UnsafePointer<Int8>> = UnsafePointer(cs)

matt Over a year ago

Why do you want to make the inner pointers mutable? In C strings, they are not.

Omid Yaghoubi Over a year ago

I want to use a posix function in unistd : public func execvp(_: UnsafePointer<Int8>, _: UnsafePointer<UnsafeMutablePointer<Int8>>) -> Int32

matt Over a year ago

Okay, I wrote it all out for you, but this is absolutely the last time. :)

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