[rmiller@pacific]# echo "hello world" > hello
[rmiller@pacific]# xxd hello
0000000: 6865 6c6c 6f20 776f 726c 640a hello world
So you can use this tool to byte edit files. One rather unusual use I’ve found for it is to paste in an RPM to a system that I only had serial console access to. I just ran xxd on it, copied it into the buffer, and pasted it into a file on the remote server. A quick xxd -r, and voila. RPM.
I recently ran across the above blog entry which is from 2010. All these years working with Unix systems and I never knew about this command. When I parse a web site to extract information it’s necessary to output clean and concise ASCII data for my downstream scripts. My perl scripts that html parse do filter this out but sometimes a funny character gets through. Normally I have been using hexedit to determine the hex code of the offending character and although it works, it’s not as elegant as the above xxd command. Now I can do the following:
xxd offendingdatafile.txt | grep "mystring" | more
The above should simply output lines containing the offending hexcode using grep if I kind of notice a unique searchable string (mystring) before the offending hex character. I could also:
xxd offendingdatafile.txt > myfile.dat
Instead of using clunky hexedit to search for mystring I can use good old vi.
I’m sure there are lots of other uses for this utility — especially in shell scripts. Unix has so many commands and I utilize a subset adequate to getting whatever it is I need to do. Every year I pick up one or two new useful commands that are more efficient and xxd is one of them.