Once in a while I need to know what characters are in a file and how often each appears. One reason I might do this is to look for statistical anomalies. Another reason might be to see whether a file has any characters it’s not supposed to have, which is often the case.
A few days ago Fatih Karakurt left an elegant solution to this problem in a comment:
fold -w1 file | sort | uniq -c
The fold function breaks the content of a file in to lines 80 characters long by default, but you can specify the line width with the -w option. Setting that to 1 makes each character its own line. Then sort prepares the input for uniq, and the -c option causes uniq to display counts.
This works on ASCII files but not Unicode files. For a Unicode file, you might do something like the following Python code.
import collections
count = collections.Counter()
file = open("myfile", "r", encoding="utf8")
for line in file.readlines():
for c in line.strip("\n"):
count[ord(c)] += 1
for p in sorted(list(count)):
print(chr(p), hex(p), count[p])