===== Task =====
Given a bunch of files in a directory, count the number of times a word occurs in each file. For example, given

<code>
% tail -n +1 *
==> junk1.txt <==
foo
bar
foo bar foo
bar foo bar

==> junk2.txt <==
foo
bar
foo bar foo
bar foo bar
foo foo foo
</code>

count the number of occurrences of 'foo' in each file. The expected answer is
<code>
junk1.txt:4
junk2.txt:7
</code>

tags | Number of matches per file

sample code demoes | cat with filename
===== Solution using git grep and awk =====
If it is a git repository
<code>
git grep -o foo  | awk -F':' '{freq[$1]++} END{for (file in freq) print file ":" freq[file]}'
</code>

If it is not a git repository
<code>
git grep --no-index -o foo  | awk -F':' '{freq[$1]++} END{for (file in freq) print file ":" freq[file]}'
</code>

For example
<code>
% git grep --no-index -o foo  | awk -F':' '{freq[$1]++} END{for (file in freq) print file ":" freq[file]}'
junk2.txt:7
junk1.txt:4
</code>

==== How it works ====
The git grep command gives
<code>
% git grep --no-index -o foo
junk1.txt:foo
junk1.txt:foo
junk1.txt:foo
junk1.txt:foo
junk2.txt:foo
junk2.txt:foo
junk2.txt:foo
junk2.txt:foo
junk2.txt:foo
junk2.txt:foo
junk2.txt:foo
</code>
The awk command counts the number of hits per file.

==== References ====
  * https://stackoverflow.com/questions/39945363/frequency-count-for-file-column-in-bash - count frequencies using awk

==== tags ====
awk frequency count, awk count breakdown, uniq reverse output, "git grep" count matches, count "grep -o", "grep -o" counts, "grep -o" summarize

===== Solution using grep and awk =====
<code>
grep -ro foo * | awk -F':' '{freq[$1]++} END{for (file in freq) print file ":" freq[file]}'
</code>

Useful if git is not available.
===== Solution using find, grep and wc =====
<code>
find * -printf 'echo "%p:$(grep -o "foo" %p | wc -l)";' | sh
</code>

For example
<code>
% find * -printf 'echo "%p:$(grep -o "foo" %p | wc -l)";' | sh
junk1.txt:4
junk2.txt:7
</code>

==== How it works ====
To see how it works, run the command without piping the output to sh
<code>
% find * -printf 'echo "%p:$(grep -o "foo" %p | wc -l)";'     
echo "junk1.txt:$(grep -o "foo" junk1.txt | wc -l)";echo "junk2.txt:$(grep -o "foo" junk2.txt | wc -l)";
</code>

So we are just building up a big command that would run "grep -o" on each file and then format the output.

<code>
find *          - find the files
-printf ''      - format and print everything between the single-quotes.
%p in -printf   - will be replaced by the filename in find's output
grep -o         - print only the matched (non-empty) parts of a matching line, with each such part on a separate output line.
| sh            - execute the command
</code>

Note: You have to use "grep -o" and not "grep -c". If a string occurs multiple times in a line, "grep -o" matches each of them separately. But "grep -c" counts them together. For example

<code>
% cat junk2.txt 
foo
bar
foo bar foo
bar foo bar
foo foo foo

% grep foo junk2.txt
foo
foo bar foo
bar foo bar
foo foo foo

% grep -o foo junk2.txt 
foo
foo
foo
foo
foo
foo
foo

% grep -c foo junk2.txt
4

% grep -o foo junk2.txt| wc -l
7
</code>

==== References ====
  * https://newbedev.com/counting-all-occurrences-of-a-string-within-all-files-in-a-folder - where I came across this solution.