Extract filename - unix

Question

So I am new to SED and Unix and I would like to replace the following file:
1500:../someFile.C:111 error
1869:../anotherFile.C:222 error
1869:../anotherFile2.Cxx:333 error
//thousands of more lines with same structure
With the followig file
someFile.c
anotherFile.c
anotherFile2.Cxx
Basically, I just want to extract the filename from every line.
So far, I have read the documentation on sed and the second answer here. My best attempt was to use a regex as follows:
sed "s/.\*\/.:.*//g" myFile.txt

Answer 1

Lots of ways to do this.
Sure, you could use sed:
sed 's/^[^:]*://;s/:.*//;s#\.\./##' input.txt
sed 's%.*:\.\./\([^:]*\):.*%\1%' input.txt
Or you could use a series of grep -o instances in a pipe:
grep -o ':[^:]*:' input.txt | grep -o '[^:]\{1,\}' | grep -o '/.*' | grep -o '[^/]\{1,\}'
You could even use awk:
awk -F: '{sub(/\.\.\//,"",$2); print $2}' input.txt
But the simplest way would probably be to use cut:
cut -d: -f2 input.txt | cut -d/ -f2

Answer 2

You can capture the substring between last / and following : and replace the whole string with the captured string(\1).
sed 's#.*/\([^:]\+\).*#\1#g' myFile.txt
someFile.C
anotherFile.C
anotherFile2.Cxx
OR , with little less escaping, sed with -r flag.
sed -r 's#.*/([^:]+).*#\1#g' myFile.txt
Or if you want to use grep,this will only work if your grep supports -P flag which will enable PCRE:
grep -oP '.*/\K[^:]+' myFile.txt
someFile.C
anotherFile.C
anotherFile2.Cxx