Appending two text (non-data) files together

[Richard Williams]

I have a program that is writing out code that will eventually be used in a different software package. The code gets written in separate pieces, and unfortunately the logic is such that I can't just generate the pieces in the order I eventually want them to be in. Once done, I want to combine the pieces in the correct order, e.g. if one tempory file is called front and another is called back I want to combine them into frontback.

Interactively this takes the better part of 30 seconds of copy and paste. But I would rather just have Stata generate everything in a single piece.

I am thinking I could open the final output file as read write and then do file read and write commands (basically copying the files one line at a time into a new file) but is there something simpler? If these were data files I could just use the append command but if such an easy solution exists it is currently eluding me.

[Clyde Schechter]

Well if you're running Windows you can open a command window (-shell- from within Stata) and run

copy file1+file2 destinationfile

(You can append as many files as you like with more "terms" connected by + signs.)

Or, again in Windows, you can do

type file2 >> file1

and file1 will now have the contents of file2 appended to it.

[Richard Williams]

Thanks! That is certainly simple. But I would like something that would work on other operating systems too. The other software, Mplus, works on

Operating Systems

• Microsoft Windows 7/8/10
• Mac OS X 10.8 or later
• Linux (tested on the following distributions: Ubuntu, RedHat, Fedora, Debian, and Gentoo)

[William Lisowski]

In the past I've done something similar by writing my temporary files as Stata data files containing a single string variable, called, say, line. Then I use Stata to append them in the appropriate order, and the write the appended file as a text file.

Alternatively, on Mac and Linux systems, text files can be appended in a shell window with

cat file1 file2 > destinationfile

and

cat file2 >> file1

as in Clyde's examples.

[Richard Williams]

Clyde's tip works! Or at least the version using the type command does.

If I do -creturn list- the values include

c(os) = "Windows"

I am guessing I could do some sort of OS check and then use William's command for Mac and Unix.

Thanks for the great help. Thanks to you two I have a fighting chance of getting to bed at a decent hour tonight.

[Richard Williams]

I rewrote the code as follows. It works ok in Windows but I don't have a Mac or Unix machine to test it on. Does it look ok? I have this feeling I should eventually come up with code that doesn't rely on OS calls at all but for now this is pretty easy.

    if "`c(os)'" == "Windows" {
        shell type `xback' >> `mfilename'.inp
    }
    else if "`c(os)'" == "MacOSX" {
        shell cat `xback' >> `mfilename'.inp
    }
    else if "`c(os)'" == "Unix" {
        shell cat `xback' >> `mfilename'.inp
    }

[Clyde Schechter]

That looks like it should work. You might want to make it a little more compact:

if "`c(os)'" == "Windows" {
    local command type
}
else if inlist("`c(os)'", "MacOSX", "Unix") {
    local command cat
}

shell `command' `xback' >> `mfilename'.inp

though I think people might disagree as to which version is more readily understandable.

[Richard Williams]

Thanks. Yes, I went for readability over compactness, mostly in case I need to change the code in the next 10 years.

[William Lisowski]

Works as I expected on MacOSX. We hope that with the forthcoming rebranding of Mac OS X to macOS, Stata does not follow suit, or lots of OS-specific code will fail on Macs.

If I were interested in tight code, I would tighten Clyde's code even further, by recognizing that Windows is the only operating system lacking UNIX underpinnings:

local command cat
if "`c(os)'" == "Windows" {
    local command type
}

shell `command' `xback' >> `mfilename'.inp

[Richard Williams]

Thanks William. Yes, I would rather not have OS specific code but I would also rather have some time to do other things today. I'm guessing Windows will be with us for all eternity so maybe something like your code is safest. So I rewrote the code like this:

    if "`c(os)'" == "Windows" {
        shell type `xback' >> `mfilename'.inp
    }
    else shell cat `xback' >> `mfilename'.inp