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I am given an assignment like this: Write a Bash script that takes a *.tex file as command-line argument and checks if the file executes correctly without any errors. If it executes without any error and warning, assign a mark of 2 to that file. (1 mark if it compiled with a warning, and 0 marks if it shows an error).

I am able to assign marks for files which executed without any warnings and for files which gave a warning. Here, I am giving some of the lines of my code,

rm t.txt
pdflatex $1 >> t.txt
message=`tail -2 t.txt|grep -i "output"|cut -c 1-6`

After executing the command pdflatex, my script searches for appropriate words like "output" and "warning", and accordingly assigns marks. But in the case of a file which has errors, the pdflatex command exits only if we give a 'x'. Since it is expecting an 'x' from the user, it waits there. If I run the script, it is not showing any output; but if I print an x, it assigns the mark to that file as zero.

But I have to give this program to an automatic code-evaluator which checks for my code, and tells if my code is correct for all the cases...

How do I accomplish that?

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Workaround: tell pdflatex to behave, using -interaction nonstopmode. – Stéphane Gimenez Dec 1 '11 at 14:32

Tell pdflatex not to wait for any interactive input ever:

pdflatex -interaction nonstopmode "$1"

If the command returns a nonzero status ($?), there was an error, so the mark is 0. Otherwise, test whether the log file (like $1, but with .log instead of the extension that's there already) contains the word Warning; if it does, the mark is 1, otherwise the mark is 0.

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In the general case, if you have a program in a shell script that tries to read input from the user, you can stop that by adding this at the top of your script:

exec < /dev/null

This tells the script to read input from /dev/null instead of from the keyboard. If any command after that tries to read input, it will immediately receive end-of-file.

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