ecpg

Preprocess a specific file

$ ecpg [input.pgc]

$ ecpg -o - -

$ cat input.pgc | ecpg -o output.c -

$ ecpg -o [output.c] [input.pgc]

$ ecpg [input.pgh]

$ ecpg -C [INFORMIX|INFORMIX_SE|ORACLE] [input.pgc]

$ ecpg -t [input.pgc]

ecpg [option...] inputfile

-I directory
    Add directory to path for searching INCLUDE files.

-L directory
    Add directory to library search path.

-l library
    Add library to link line (e.g., -lpq).

-o filename
    Specify output file name (default: input.ecpg.c).

-v
    Enable verbose mode for detailed processing info.

-t
    Enable minimal runtime debugging.

-c
    Enable compatibility mode for older ECPG syntax.

-E
    Display errors only, suppress warnings.

-R {no|full|include|location|statement}
    Control error reporting detail level.

-i
    Ignore missing INCLUDE files.

--include-any
    Allow includes from any directory.

--include-first
    Search current directory before system paths.

--version
    Print version information.

-? | --help
    Show help message.

ecpg is the embedded SQL preprocessor for PostgreSQL, transforming C source files with embedded SQL statements into standard C code.

It processes directives like EXEC SQL followed by SQL commands, replacing them with calls to the libpq library. This enables seamless integration of SQL queries, DDL, DML, transactions, cursors, and dynamic SQL within C programs.

Key features include support for host variables (using : prefix), indicator variables, error handling via WHENEVER clauses, and type conversion between SQL and C data types. The preprocessor generates an output file (default: input.ecpg.c) that can be compiled with a C compiler like gcc, linking against libecpg and libpq.

Typical workflow: Write C code with embedded SQL, run ecpg input.c, then gcc -I$(pg_config --includedir) input.ecpg.c -lecpg -lpq -o program. It enforces SQL standards (e.g., SQL:1999) and provides debugging options for verbose output and error reporting.

ecpg is essential for database-intensive C applications, offering performance benefits over string-based queries while maintaining portability within PostgreSQL environments. (187 words)

Requires PostgreSQL development packages (e.g., libecpg-dev). Output must be compiled with PostgreSQL libs; mismatched versions cause linking errors.
Not thread-safe by default; use -t for debugging.

After ecpg foo.pgc:
gcc $(pg_config --cflags) foo.ecpg.c $(pg_config --libs) -lecpg -o foo

Use EXEC SQL SELECT ... INTO :hostvar; with WHENEVER SQLERROR GOTO label; for control flow.

Introduced in PostgreSQL 6.3 (1998) as open-source ECPG, originally from Ingres. Evolved with SQL standards support; current versions align with PostgreSQL 16+ features like advanced cursors and error handling.

psql(1), pg_config(1), gcc(1), libpq(3)