Merge pdf files with numerical sort

Question

I am trying to write a bash script to merge all pdf files of a directory into one single pdf file. The command pdfunite *.pdf output.pdf successfully achieves this

Answer 1

you can embed the result of command using $(), so you can do following

$ pdfunite $(ls -v *.pdf) output.pdf

or

$ pdfunite $(ls *.pdf | sort -n) output.pdf

However, note that this does not work when filename contains special character such as whitespace.

In the case you can do the following:

ls -v *.txt | bash -c 'IFS=$'"'"'\n'"'"' read -d "" -ra x;pdfunite "${x[@]}" output.pdf'

Although it seems a little bit complicated, its just combination of

• Bash: Read tab-separated file line into array
• build argument lists containing whitespace
• How to escape single-quotes within single-quoted strings?

Note that you cannot use xargs since pdfunite requires input pdf's as the middle of arguments. I avoided using readarray since it is not supported in older bash version, but you can use it instead of IFS=.. read -ra .. if you have newer bash.

Answer 2

You can rename your documents i.e. 001.pdf 002.pdf and so on.

Answer 3

Do it in multiple steps. I am assuming you have files from 1 to 99.

 pdfunite $(find ./ -regex ".*[^0-9][0-9][^0-9].*"  | sort) out1.pdf
 pdfunite out1.pdf $(find ./ -regex ".*[^0-9]1[0-9][^0-9].*"  | sort) out2.pdf
 pdfunite out2.pdf $(find ./ -regex ".*[^0-9]2[0-9][^0-9].*"  | sort) out3.pdf

and so on.

the final file will consist of all your pdfs in numerical order.

!!! Beware of writing the output file such as out1.pdf etc. otherwise pdfunite will overwrite the last file !!!

Edit: Sorry I was missing the [^0-9] in each regex. Corrected it in the above commands.