Specifying the Source File
Go Up to Preprocessing
Contents
Because both the language switch and the filename extension are optional, gpre
can encounter three different situations:
- A language switch and input file with no extension
- No language switch, but an input file with extension
- Neither a language switch, nor a file extension
This section describes gpre
’s behavior in each of these cases.
Language Switch and No Input File Extension
If gpre
encounters a language switch, but the specified input file has no extension, it does the following:
- It looks for the input file without an extension. If
gpre
finds the file, it processes it and generates an output file with the appropriate extension. Ifgpre
does not find the input file, it looks for the file with the extension that corresponds to the indicated language. If it finds such a file, it generates an output file with the appropriate extension. - If
gpre
cannot find either the named file or the named file with the appropriate extension, it returns the following error:gpre: can’t open filename or filename.extension
<filename> is the file specified in the
gpre
command. <extension> is the language-specific file extension for the specified program.
An Example:
Suppose the following command is issued:
gpre -c census
gpre
performs the following sequence of actions:
- It looks for a file called
census
without an extension. If it finds the file, it processes it and generatescensus.c
. - If it cannot find
census
, it looks for a file calledcensus.e
. If it findscensus.e
, it processes the file and generatescensus.c
. - If it cannot find
census
orcensus.e
, it returns this error:
gpre: can’t open census or census.e
An Input File with Extension by No Language Switch
If a language switch is not specified, but the input file includes a file-name extension, gpre
looks for the specified file and assumes the language is indicated by the extension.
For example, suppose the following command is processed:
gpre census.e
gpre
looks for a file called census.e
. If gpre
finds this file, it processes it as a C program and generates an output file called census.c
. If gpre
does not find this file, it returns the following error:
gpre: can’t open census.e
Neither a Language Switch Nor a File Extension
If gpre
finds neither a language extension nor a filename extension, it looks for a file in the following order:
filename.e
(C)filename.epas
(Pascal)filename.ef
(FORTRAN
)filename.ecob
(COBOL
)filename.ea
(VERDIX
Ada)filename.eada
(Alsys, and Telesoft Ada)
If gpre
finds such a file, it generates an output file with the appropriate extension. If gpre
does not find the file, it returns the following error:
gpre: can’t find filename with any known extension. Giving up.