replace a part of a string with REGEXP in sqlite3 - regex

Question

I installed REGEX support with
apt-get install sqlite3 sqlite3-pcre
now I can use REGEX in my queries on the bash console like
DB="somedb.db"
REGEX_EXTENSION="SELECT load_extension('/usr/lib/sqlite3/pcre.so');"
sqlite3 $DB "$REGEX_EXTENSION select * from sometable where name REGEXP '^[a-z]+$'"
But how can I update a string with an sqlite query using regex?

Answer 1

Sqlite by default does not provide regex_replace function. You need to load it as an extension. Here is how i managed to do it.
Download this C code for the extension (icu_replace)
Compile it using
gcc --shared -fPIC -I sqlite-autoconf-3071100 icu_replace.c -o icu_replace.so
And in sqlite3 runn following command post above mentioned command has run and create a file icu_replace.so
SELECT load_extension(' path to icu_replace.so', 'sqlite3_extension_init') from dual;
After this you will be able to use such a function as :-
select regex_replace('\bThe\b',x,'M') from dual;

Answer 2

The following builds latest sqlite with dynamic library support, and compiles ICU extension and regex_replace extension. It also assumes debian-based linux distributive:
sudo apt build-dep sqlite3 # fetches dependencies to compile sqlite3
mkdir sqlite-compilation
cd sqlite-compilation
wget -O sqlite.tar.gz https://www.sqlite.org/src/tarball/sqlite.tar.gz?r=release
tar xzf sqlite.tar.gz
mkdir build
cd build
../sqlite/configure
make OPTS='-DSQLITE_ENABLE_LOAD_EXTENSION'
./sqlite3 -cmd 'pragma compile_options;' <<< .exit
cd -
# https://sqlite.org/src/dir?name=ext/icu
cd sqlite/ext/icu
sed -i 's/int sqlite3_icu_init(/int sqlite3_extension_init(/' icu.c
sed -i 's/int sqlite3IcuInit(/int sqlite3_extension_init(/' sqliteicu.h
gcc -g -O2 -shared icu.c -fPIC -I ../../../build `pkg-config --libs icu-i18n` -o libSqlite3Icu.so
cp libSqlite3Icu.so ../../../build/
cd -
# https://github.com/gwenn/sqlite-regex-replace-ext
cd sqlite/ext
wget -O sqlite-regex-replace-ext-master.zip https://github.com/gwenn/sqlite-regex-replace-ext/archive/master.zip
unzip sqlite-regex-replace-ext-master.zip
cd sqlite-regex-replace-ext-master
gcc -g -O2 -shared icu_replace.c -fPIC -I ../../../build -o libSqlite3IcuReplace.so
cp libSqlite3IcuReplace.so ../../../build/
cd -
cd ../../
In result you will have:
build/sqlite3 # sqlite3 binary
build/libSqlite3Icu.so # unicode support
build/libSqlite3IcuReplace # regex_replace function
Test:
cd build
sqlite3 <<< "
.load ./libSqlite3Icu
.load ./libSqlite3IcuReplace
select regex_replace('^a', 'aab', 'b');
.exit
" # should output: bab
cd -

Answer 3

For me the above answers didn't work because of some missing parameters in the gcc command.
This works for me:
git clone https://github.com/gwenn/sqlite-regex-replace-ext.git
cd sqlite-regex-replace-ext-master/
./icu_replace.sh
Now you should be able to load the extension using: SELECT LOAD_EXTENSION('path-to-icu_replace.so');