Make cat interpret input as file (not string)

Question

cat has two different behaviours depending on if its input is a string of file. I need to use cat to pipe a file to my PDF viewer (Zathura). The file name is based on a modified string with sed as follow:

cat <(echo test.tex | sed 's/[^.]*$/pdf/') | zathura -

I want this one liner to convert a file name string test.tex to test.pdf and pipe it to Zathura to open the corresponding file. The above command line is not working because the cat input is interpreted as a string and not as a file.

Obviously,

echo test.tex | sed 's/[^.]*$/pdf/') | zathura

is not working, that's why I try to mess around with cat.

Answer 1

Don't you mean:

cat $(echo test.tex | sed 's/[^.]*$/pdf/') | zathura -

So that the result of your sed is an argument to cat and not its stdin.

You can also use:

cat $(basename $file .tex).pdf | zathura -

or

cat ${file%.*}.pdf | zathura -

Answer 2

I don't recommend opening a file via STDIN with a document viewer that offers features such as automatic document update or SyncTeX. Doing so breaks the link between the original file and the software, since the opened file will be a copy of the original file. The displayed file will actually be something like /tmp/zathura.stdin. This can lead to security problems andy when the LaTeX source file is recompiled, the display in the software will not be updated.

So why bother with cat when you can simply pass the file name as an argument as follows:

zathura $(basename file.tex .tex).pdf

or using sed

zathura $(echo file.tex | sed 's/[^.]*$/pdf/')