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Re: st: some code that doesn't do what I expect


From   Michael Hanson <mshanson@mac.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: some code that doesn't do what I expect
Date   Tue, 8 Mar 2005 08:58:35 -0500

On Mar 8, 2005, at 12:54 AM, Philip Greenwood wrote:

. local foo "a_great_big_fish"

. save "data\`foo'.dta"
file data`foo'.dta saved

I expected `foo' to evaluate to "a_great_big_fish" in the save command.
Using a double slash fixes the problem ( i.e. -save "data\\`foo'.dta"- ).
IIRC, Stata -- like many other programming languages -- interprets the \ as an "escape" character, meaning: "rather than interpret the next character in a programming context, interpret it literally." That is, by placing \` in your command, you told Stata, "I really want a ` in the file name, rather than use the ` to signify the beginning of a macro substitution."

By using \\, you "escaped the escape" -- you told Stata: \ = "interpret the next character literally" + \ = "as a backslash", which placed the backslash in the file name. Notice that the second \ is interpreted literally instead of as an escape character, so the ` began the macro substitution as you expected.

IIFRC, Stata recognizes / as the "universal filesystem separator"; thus you could have written -save "data/`foo'.dta"- (notice: slash in other direction), and it would have worked as expected.

(Disclaimer: I don't do Windows, so I cannot test the above. I also don't have the manual in front of me, but I'm sure someone will correct any errors above. Like confusing which of \ and / is called the "backslash" -- I do that all the time....) HTH.

-- Mike

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