topic Re: X COmmand To Modify File? in SAS Programming

X COmmand To Modify File?

shl007 — Mon, 25 May 2020 05:55:14 GMT

Hi - does anyone know how to use the "X" command to modify a file? I would like to insert a line at the beginning and end of file. This would be in Unix/linux. Thanks

Re: X COmmand To Modify File?

Kurt_Bremser — Mon, 25 May 2020 07:32:22 GMT

See here: https://unix.stackexchange.com/questions/20573/sed-insert-text-after-the-last-line

It also includes the sed comnand for inserting at the top.

You can do the same thing with pure SAS means:

date _null_;
infile "file_to_read";
file "newfile" end=done;
input;
if _n_ = 1 then put "text for top";
put _infile;
if done then put "text for bottom";
run;

and then use the SAS file functions in a follow-up step to remove the old file and rename the new.

Re: X COmmand To Modify File?

shl007 — Tue, 26 May 2020 14:33:33 GMT

Yeah I tried the SAS datastep approach, but for some reason it is truncating my input line even though I'm specifying LRECL = 32767. So I'm going with the Unix command and running that through the "x" command in SAS. As such, the following x command syntax works for me in SAS to insert at the END of the file:

x 'echo "text you want to insert" >> filepath/filename'

But when I try the following syntax to insert a line at the BEGINNING of the file, it doesn't seem to work, i.e., nothing happens?

x 'echo 'sed -i '1i "text you want to insert" >> filepath/filename'

Any tips appreciated. Much thanks!

Re: X COmmand To Modify File?

Kurt_Bremser — Tue, 26 May 2020 14:44:36 GMT

The complete commandline for the sed call is this:

sed -i '1s/^/text you want to insert'\n' filepath/filename

So the SAS statements will be

x "sed -i '1s/^/text you want to insert on top'\n' filepath/filename";
x "echo 'text you want to insert at end' >> filepath/filename";

Please also post the data step code you tried.

Re: X COmmand To Modify File?

shl007 — Tue, 26 May 2020 16:48:57 GMT

Below is the data code I had tried. I am populating the filename with a macro variable set earlier (not shown). The file modification is working, just truncating certain lines for some reason.

filename output pipe "ls -a /mypath/*myfile*";

%macro create_xml;

%if &totalfiles gt 0 %then %do;
%do i=1 %to &totalfiles;
	data _null_;

     infile "&&filenm&i" lrecl=32767 end = last;

/*	moddate=finfo(fid,'Last Modified');*/

	do while(not last);
    	input;

	    file "&&fileout&i";

		if lag("&&filenm&i") ne "&&filenm&i" then do;

        	put "mytext1"; /* beginning of file */

        end;

            put _infile_;  
	end;

	if  last then do;

       		put "</root>";

	end;
 
run;
%end;
%end;
%mend create_xml;

Re: X COmmand To Modify File?

shl007 — Tue, 26 May 2020 16:51:06 GMT

Also, just to document what worked for me to insert the first line in file:

x "sed -i '1i mytext' /mypath/myfile.txt";

Re: X COmmand To Modify File?

Kurt_Bremser — Tue, 26 May 2020 18:03:53 GMT

Your data step code is much too complicated. Use mine as a blueprint.

In particular, this

if lag("&&filenm&i") ne "&&filenm&i" then do;

makes no sense, as lag cannot work with strings, only data step variables. It seems you tried to adapt code that reads filenames from a dataset and reads multiple files, but you only need to read and write a single file in one step.