Getting a list of substring based unique filenames in an array - bash

Question

I have a directory my_dir with files having names like:
a_v5.json
a_v5.mapping.json
a_v5.settings.json
f_v39.json
f_v39.mapping.json
f_v39.settings.json
f_v40.json
f_v40.mapping.json
f_v40.settings.json
c_v1.json
c_v1.mapping.json
c_v1.settings.json
I'm looking for a way to get an array [a_v5, f_v40, c_v1] in bash. Here, array of file names with the latest version number is what I need.
Tried this: ls *.json | find . -type f -exec basename "{}" \; | cut -d. -f1, but it returns the results with files which are not of the .json extension.

Answer 1

You can use the following command if your filenames don't contain whitespace and special symbols like * or ?:
array=($(
find . -type f -iname \*.json |
sed -E 's|(.*/)*(.*_v)([0-9]+)\..*|\2 \3|' |
sort -Vr | sort -uk1,1 | tr -d ' '
))
It's ugly and unsafe. The following solution is longer but can handle all file names, even those with linebreaks in them.
maxversions() {
find -type f -iname \*.json -print0 |
gawk 'BEGIN { RS = "\0"; ORS = "\0" }
match($0, /(.*\/)*(.*_v)([0-9]+)\..*/, group) {
prefix = group[2];
version = group[3];
if (version > maxversion[prefix])
maxversion[prefix] = version
}
END {
for (prefix in maxversion)
print prefix maxversion[prefix]
}'
}
mapfile -d '' array < <(maxversions)
In both cases you can check the contents of array with declare -p array.

Answer 2

Arrays and bash string parsing.
declare -A tmp=()
for f in $SOURCE_DIR/*.json
do f=${f##*/} # strip path
tmp[${f%%.*}]=1 # strip extraneous data after . in filename
done
declare -a c=( $( printf "%s\n" "${!tmp[#]}" | cut -c 1 | sort -u ) ) # get just the first chars
declare -a lst=( $( for f in "${c[#]}"
do printf "%s\n" "${!tmp[#]}" |
grep "^${f}_" |
sort -n |
tail -1; done ) )
echo "[ ${lst[#]} ]"
[ a_v5 c_v1 f_v40 ]
Or, if you'd rather,
declare -a arr=( $(
for f in $SOURCE_DIR/*.json
do d=${f%/*} # get dir path
f=${f##*/} # strip path
g=${f:0:2} # get leading str
( cd $d && printf "%s\n" ${g}*.json |
sort -n | sed -n '$ { s/[.].*//; p; }' )
done | sort -u ) )
echo "[ ${arr[#]} ]"
[ a_v5 c_v1 f_v40 ]

Answer 3

This is one possible way to accomplish this :
arr=( $( { for name in $( ls {f,n,m}*.txt ); do echo ${name:0:1} ; done; } | sort | uniq ) )
Output :
$ echo ${arr[0]}
f
$ echo ${arr[1]}
m
$ echo ${arr[2]}
n
Regards!

Answer 4

AWK SOLUTION
This is not an elegant solution... my knowledge of awk is limited.
You should find this functional.
I've updated this to remove the obsolete uniq as suggested by #socowi.
I've also included the printf version as #socowi suggested.
ls *.json | cut -d. -f1 | sort -rn | awk -v last="xx" '$1 !~ last{ print $1; last=substr($1,1,3) }'
OR
printf %s\\n *.json | cut -d. -f1 | sort -rn | awk -v last="xx" '$1 !~ last{ print $1; last=substr($1,1,3) }'
Old understanding below
Find files with name matching pattern.
Now take the second field since your results will likely be similar to ./
find . -type f -iname "*.json" | cut -d. -f2
To get the unique headings....
find . -type f -iname "*.json" | cut -d. -f2 | sort | uniq