How can I view all historical changes to a file in SVN

There's no built-in command for it, so I usually just do something like this:

#!/bin/bash

# history_of_file
#
# Outputs the full history of a given file as a sequence of
# logentry/diff pairs.  The first revision of the file is emitted as
# full text since there's not previous version to compare it to.

function history_of_file() {
    url=$1 # current url of file
    svn log -q $url | grep -E -e "^r[[:digit:]]+" -o | cut -c2- | sort -n | {

#       first revision as full text
        echo
        read r
        svn log -r$r $url@HEAD
        svn cat -r$r $url@HEAD
        echo

#       remaining revisions as differences to previous revision
        while read r
        do
            echo
            svn log -r$r $url@HEAD
            svn diff -c$r $url@HEAD
            echo
        done
    }
}

Then, you can call it with:

history_of_file $1

Slightly different from what you described, but I think this might be what you actually need:

svn blame filename

It will print the file with each line prefixed by the time and author of the commit that last changed it.

If you want to see whole history of a file with code changes :

svn log --diff [path_to_file] > log.txt

You could use git-svn to import the repository into a Git repository, then use git log -p filename. This shows each log entry for the file followed by the corresponding diff.