Invoke the ESQL/C filter
The esql command can automatically call the IBM® Informix® ESQL/C filter, esqlmf, to process non-ASCII characters.
The following figure shows how the Informix
ESQL/C program that contains non-ASCII characters becomes an executable program.
Figure 1. Create an ESQL/C executable program from a non-ASCII source program
When you set the following environment variables, you tell esql how
to invoke esqlmf:
- The ESQLMF environment variable indicates
whether esql automatically calls the Informix
ESQL/C filter.
When you set ESQLMF to 1, esql automatically calls esqlmf after the Informix ESQL/C preprocessor and before the C compiler.
- The CC8BITLEVEL environment variable indicates
the non-ASCII characters in the Informix
ESQL/C source file that esqlmf filters.
Set CC8BITLEVEL to indicate the ability of your C compiler to process non-ASCII characters.
How esqlmf filters the Informix
ESQL/C source file depends on the value of the
CC8BITLEVEL environment variable. For each value of
CC8BITLEVEL, the following table shows the esqlmf command
that the Informix
ESQL/C processor invokes on the
Informix
ESQL/C source file.
| CC8BITLEVEL | The esqlmf action |
|---|---|
| 0 | Converts all non-ASCII characters, in literal strings and comments, to octal constants. |
| 1 | Converts non-ASCII characters in literal strings, but not in comments, to octal constants. |
| 2 | Converts non-ASCII characters in literal strings to octal constants to ensure that all the bytes in the non-ASCII characters have the eighth bit set. |
| 3 | Does not invoke esqlmf. |
Important: To start the esqlmf commands that
CC8BITLEVEL can specify, you must set the ESQLMF
environment variable to 1.
When you set CC8BITLEVEL to 0, 1,
or 2, the Informix
ESQL/C processor performs
the following steps:
- Converts the embedded-language statements (source.ec) to C-language source code (source.c) with the Informix ESQL/C preprocessor
- Filters non-ASCII characters in the preprocessed
file (source.c) with the Informix
ESQL/C filter, esqlmf (if the ESQLMF environment variable is 1)
Before esqlmf begins filtering, it creates a copy of the C source file (source.c) that has the .c_ file extension (source.c_).
- Compiles the filtered C source file (source.c) with the C compiler to create an object file (source.o)
- Links the object file with the Informix ESQL/C libraries and your own libraries to create an executable program
When you set CC8BITLEVEL to 3, the Informix ESQL/C processor omits step 2 in the preceding list.
If you do not set CC8BITLEVEL, then esql converts non-ASCII characters in literal strings and comments. You can modify the value of CC8BITLEVEL to reflect the capabilities of your C compiler.