Fastest way to tell if two field have the same contents in Unix/Linux?

linux file unix diff
JDS picture JDS · Oct 15, 2012 · Viewed 199.4k times · Source

I have a shell script in which I need to check whether two fields contain the same data or not. I do this a for a lot of files, and in my script the diff command seems to be the performance bottleneck.

Here's the line:

diff -q $dst $new > /dev/null

if ($status) then ...

Could there be a faster way to compare the files, maybe a custom algorithm instead of the default diff?

Answer

Alex Howansky picture Alex Howansky · Oct 15, 2012

I believe cmp will stop at the first byte difference:

cmp --silent $old $new || echo "files are different"

Related questions

How to get full path of a file?

Is there an easy way I can print the full path of file.txt ? file.txt = /nfs/an/disks/jj/home/dir/file.txt The <command> dir> <command> file.txt should print /nfs/an/disks/…

Read More
How can I convert a file pointer ( FILE* fp ) to a file descriptor (int fd)?

I have a FILE *, returned by a call to fopen(). I need to get a file descriptor from it, to make calls like fsync(fd) on it. What's the function to get a file descriptor from a file pointer?

Read More
Truncating a file while it's being used (Linux)

I have a process that's writing a lot of data to stdout, which I'm redirecting to a log file. I'd like to limit the size of the file by occasionally copying the current file to a new name and truncating …

Read More