CRE Programmer's Guide

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Common Run-Time Environment (CRE) Programmer’s Guide—528146-004

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Determining When Standard Files Are Opened

The language in which the main routine is written determines when and if standard files

are opened. If the main routine is written in C, the C run-time library opens the three

standard files as part of program initialization unless the C main routine specifies the

nostdfiles pragma. If the main routine is written in COBOL, FORTRAN, or TAL,

standard files are opened only when routines in those languages explicitly execute a

statement that opens a standard file.

If a program contains C routines and the main routine is not written in C, one of the C

routines must open explicitly each standard file before any C routine in the program

accesses that standard file. You open standard files in C by calling the C library

function fopen_std_file():

fopen_std_file( file, die_on_error )

fopen_std_file() opens a connection to a standard file.

The Guardian TNS C Library Calls Reference Manual describes the

fopen_std_file() library function.

See the reference manual for each language for further information on opening

standard files.

Using Terminals and Process

If the physical file specified for standard input is the same as the physical file specified

for either standard output or standard log (or both), and the device type of standard

input is either a terminal or a process (but not a spooler collector), the CRE opens the

specified file only once and uses the same operating system file open when your

program reads from standard input or writes to standard output or standard log.

Program Startup Message

When your program begins execution, the CRE reads the startup message sent to it by

the process that starts your program. The discussions that follow frequently reference

two of the fields of the startup message: INFILE and OUTFILE. Figure 2-10

shows the

locations of INFILE and OUTFILE in the startup message. The Guardian Programmer’s

Guide describes all of the fields in the startup message.