How to overwrite a UNIX file?

Question

How to overwrite a UNIX file?

There is a code you need to overwrite the result on the same file

exec ('sort-u-b-n 1.txt > uTest_1.txt');

Now overwrites in uTest_1.txt and you need to 1.txt

* nix-like systems

eldon_Denesik asked September 19th 19 at 00:12

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2 answers

cullen.Jast40 answered on · Answer 1 · 2019-09-19T00:14:05.408Z

cullen.Jast40 answered on September 19th 19 at 00:14

And so:
exec ('sort-u-b-n 1.txt -o 1.txt');
-o - that specify the file where to save the result. On the screen nothing will happen

or this:

exec ('sort-u-b-n 1.txt > uTest_1.txt && mv uTest_1.txt 1.txt');

and what to do about the pipeline? it seems to me that it is more correct to use ; or && - arlene_Lebsa commented on September 19th 19 at 00:17

: Yes, was in a hurry... Corrected )) - cullen.Jast40 commented on September 19th 19 at 00:20

Carrol answered on · Answer 2 · 2019-09-19T00:16:05.410Z

Carrol answered on September 19th 19 at 00:16

In the General case -- can only write to a temporary file and then rename it.
In the particular case of sort you can use -o, which here explicitly says that the name of the file to match the name of one of the input files. (But not always, particularly in the presence of the-m switch to gnu sort may overwrite the input file before it is read).