Convert mSQL C Source Safely with msql2mysql

msql2mysql rewrites the C source file you give it in place, with no dry run and no output-file option, so the backup step below is not optional. This gets you a converted copy of an mSQL C program, a preserved original, and a quick way to review exactly what changed.

Allow about ten minutes for a small file, plus whatever time you need to review and compile the result. You need a shell, a C source file using the mSQL API, and the mariadb-client package. The examples use the installed MariaDB 10.11.14 client utilities on Ubuntu 24.04; check your own package version before relying on exact details.

1. Check the installed command

An ordinary read-only check, no sudo needed:

$ command -v msql2mysql
/usr/bin/msql2mysql
$ dpkg-query -W -f='${Package} ${Version}\n' mariadb-client
mariadb-client 1:10.11.14-0ubuntu0.24.04.1

The local manpage shows the syntax as msql2mysql C-source-file .... It documents file operands, not a dry-run or output-file option. Treat any invocation as a change to every named source file.

2. Make a recoverable copy

Pick the file to convert, replace /path/to/client-prog.c with the real path, then make a separate original alongside it:

$ cp -- /path/to/client-prog.c /path/to/client-prog.c.orig
$ cmp -- /path/to/client-prog.c /path/to/client-prog.c.orig

A successful cmp prints nothing and returns status 0. If it reports a difference, stop and work out which file is the trusted original before continuing.

$ cp -- /path/to/client-prog.c.orig /path/to/client-prog.c

That overwrites the converted working file, so check both paths carefully before pressing Enter.

3. Convert the source file

Run the command with the source path as its operand:

$ msql2mysql /path/to/client-prog.c
/path/to/client-prog.c converted

• Skip --. This installed command passes its operands straight to the underlying replacement utility, and a literal -- gets treated as a file name rather than a documented option separator.
• The message names the file that changed. The utility converts mSQL C API calls to their MySQL equivalents and rewrites the mSQL header name too. On this MariaDB 10.11 install, a small test containing msql_query, msqlFetchRow and msqlStoreResult came out as mysql_query, mysql_fetch_row and mysql_store_result, with m_result changed to MYSQL_RES.
• Several files can be given at once. The documented synopsis accepts one or more C source files, but each named file still gets changed in place, so back up every one of them.

$ cp -- client-a.c client-a.c.orig
$ cp -- client-b.c client-b.c.orig
$ msql2mysql client-a.c client-b.c
client-a.c converted
client-b.c converted

4. Review the rewrite before compiling

A conversion message is not proof the program is ready. Diff the converted file against its backup:

$ diff -u -- client-prog.c.orig client-prog.c
--- client-prog.c.orig
+++ client-prog.c
@@
-#include <msql.h>
+#include <mysql.h>
@@
-  msqlFetchRow(result);
+  mysql_fetch_row(result);

Your diff will differ. Look for calls whose surrounding logic needs more than a name change: result handling, connection setup, error handling, header or library choices. The utility performs substitutions; it does not understand your program's control flow, and it does not prove the two APIs behave identically for every call.

5. Compile or run the project's checks

Use the project's normal build command after reviewing the diff. A generic example, only useful once the paths match your installation:

$ cc -Wall -Wextra -I/path/to/mysql/include -c client-prog.c -o client-prog.o

Do not copy that command unchanged unless those paths are real and the source is otherwise ready to compile. A compiler error is useful feedback about remaining API or build changes, not a reason to go and edit the backup.

6. Recover or repeat safely

If review or the build shows the rewrite is unsuitable, restore the original and verify it:

$ cp -- client-prog.c.orig client-prog.c
$ cmp -- client-prog.c client-prog.c.orig

To try again, make a fresh backup of the restored source before running msql2mysql once more. Do not use a converted file as the only input for repeated experiments: the substitutions are not a substitute for source control or a clean baseline.