Document revision date: 15 July 2002
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Compaq C
Run-Time Library Reference Manual for OpenVMS Systems
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decc$from_vms

Converts OpenVMS file specifications to UNIX style file specifications.

Format

#include <unixlib.h>

int decc$from_vms (const char *vms_filespec, int action_routine, int wild_flag);

Arguments

vms_filespec

The address of a null-terminated string containing a name in OpenVMS file specification format.

action_routine

The address of a routine that takes as its only argument a null-terminated string containing the translation of the given OpenVMS file name to a valid UNIX style file name.

If the action_routine returns a nonzero value (TRUE), file translation continues. If it returns a zero value (FALSE), no further file translation takes place.

wild_flag

Either 0 or 1, passed by value. If a 0 is specified, wildcards found in vms_filespec are not expanded. Otherwise, wildcards are expanded and each one is passed to action_routine. Only expanded file names that correspond to existing UNIX style files are included.

Description

The decc$from_vms routine converts the given OpenVMS file specification into the equivalent UNIX style file specification. It allows you to specify OpenVMS wildcards, which are translated into a list of corresponding existing files in UNIX style file specification format.

Return Value

x The number of file names that result from the specified OpenVMS file specification.

Example


/* This example must be run as a foreign command        */ 
/* and be supplied with a VMS file specification        */ 
 
#include <unixlib.h> 
#include <stdio.h> 
 
int main(int argc, char *argv[]) 
{ 
    int number_found;           /* number of files found */ 
    int print_name();           /* name printer          */ 
 
    printf("Translating: %s\n", argv[1]); 
    number_found = decc$from_vms(argv[1], print_name, 1); 
    printf("\n%d files found", number_found); 
} 
 
/* print the name on each line */ 
print_name(char *name) 
{ 
    printf("\n%s", name); 
    /* will continue as long as success status is returned */ 
    return (1); 
}

This example shows how to use the decc$from_vms routine in Compaq C. It produces a simple form of the ls command that lists existing files that match an OpenVMS file specification supplied on the command line. The matching files are displayed in UNIX style file specification format.

decc$match_wild

Matches a string to a pattern.

Format

#include <unixlib.h>

int decc$match_wild (char *test_string, char *string_pattern);

Arguments

test_string

The address of a null-terminated string.

string_pattern

The address of a string containing the pattern to be matched. This pattern can contain wildcards (such as asterisks (*), question marks (?), and percent signs (%) as well as regular expressions (such as the range [a-z]).

Description

The decc$match_wild routine determines whether the specified test string is a member of the set of strings specified by the pattern.

Return Values

1 (TRUE) The string matches the pattern.
0 (FALSE) The string does not match the pattern.

Example


/* Define as a foreign command and then provide two arguments  */ 
/* match_wild string_to_test pattern                           */ 
 
#include <unixlib.h> 
#include <stdio.h> 
int main(int argc, char *argv[]) 
{ 
    if (decc$match_wild(argv[1], argv[2])) 
        printf("\n%s matches %s", argv[1], argv[2]); 
    else 
        printf("\n%s does not match %s", argv[1], argv[2]); 
}

decc$record_read

Reads a record from a file.

Format

#include <stdio.h>

int decc$record_read (FILE *fp, void *buffer, int nbytes);

Arguments

fp

A file pointer. The specified file pointer must refer to a file currently opened for reading.

buffer

The address of contiguous storage in which the input data is placed.

nbytes

The maximum number of bytes involved in the read operation.

Description

The decc$record_read function is specific to OpenVMS systems and should not be used when writing portable applications.

This function is equivalent to the read function, except that the first argument is a file pointer, not a file descriptor.

Return Values

x The number of characters read.
- 1 Indicates a read error, including physical input errors, illegal buffer addresses, protection violations, undefined file descriptors, and so forth.

decc$record_write

Writes a record to a file.

Format

#include <stdio.h>

int decc$record_write (FILE *fp, void *buffer, int nbytes);

Arguments

fp

A file pointer. The specified file pointer must refer to a file currently opened for writing or updating.

buffer

The address of contiguous storage from which the output data is taken.

nbytes

The maximum number of bytes involved in the write operation.

Description

The decc$record_write function is specific to OpenVMS systems and should not be used when writing portable applications.

This function is equivalent to the write function, except that the first argument is a file pointer, not a file descriptor.

Return Values

x The number of bytes written.
- 1 Indicates errors, including undefined file descriptors, illegal buffer addresses, and physical I/O errors.

decc$set_child_standard_streams

For a child spawned by a function from the exec family of functions, associates specified file descriptors with a child's standard streams: stdin , stdout , and stderr .

Format

#include <unistd.h>

int decc$set_child_standard_streams (int fd1, int fd2, int fd3);

Arguments

fd1

The file associated with this file descriptor in the parent process is associated with file descriptor number 0 ( stdin ) in the child process. If - 1 is specified, the file associated with the parent's file descriptor number 0 is used (the default).

fd2

The file associated with this file descriptor in the parent process is associated with file descriptor number 1 ( stdout ) in the child process. If - 1 is specified, the file associated with the parent's file descriptor number 1 is used (the default).

fd3

The file associated with this file descriptor in the parent process is associated with file descriptor number 2 ( stderr ) in the child process. If - 1 is specified, the file associated with the parent's file descriptor number 2 is used (the default).

Description

The decc$set_child_standard_streams function allows mapping of specified file descriptors to the child's stdin/stdout/stderr streams, thereby compensating, to a certain degree, the lack of a real fork function on OpenVMS systems.

On UNIX systems, the code between fork and exec is executed in the context of the child process: 


parent: 
  create pipes p1, p2 and p3 
  fork 
child: 
  map stdin to p1  like dup2(stdin,  p1); 
  map stdout to p2 like dup2(stdout, p2); 
  map stderr to p3 like dup2(stderr, p3); 
  exec (child reads from stdin and writes to stdout and stderr) 
  exit 
parent: 
  communicates with the child using pipes

On OpenVMS systems, the same task could be achieved as follows: 


parent: 
  create pipes p1, p2 and p3 
  decc$set_child_standard_streams(p1, p2, p3); 
  vfork 
  exec (child reads from stdin and writes to stdout and stderr) 
parent: 
  communicates with the child using pipes

Once established through the call to decc$set_child_standard_streams , the mapping of the child's standard streams remains in effect until explicitly disabled by one of the following calls: 


decc$set_child_standard_streams(-1, -1, -1); 
 
   OR 
 
decc$set_child_standard_streams(0, 1, 2);

Usually, the child process inherits all its parent's open file descriptors. However, if file descriptor number n was specified in the call to decc$set_child_standard_streams , it is not inherited by the child process as file descriptor number n; instead, it becomes one of the child's standard streams.

Notes
  • Standard streams can be redirected only to pipes.
  • If the parent process redefines the DCL DEFINE command, this redefinition is not in effect in a subprocess with user-defined channels. The subprocess always sees the standard DCL DEFINE command.
  • It is the responsibility of the parent process to consume all the output written by the child process to stdout and stderr . Depending on how the subprocess writes to stdout and stderr ---in wait or nowait mode -- the subprocess might be placed in LEF state waiting for the reader. For example, DCL writes to SYS$OUTPUT and SYS$ERROR in a wait mode, so a child process executing a DCL command procedure will wait until all the output is read by the parent process.

    Recommendation: Read the pipes associated with the child process' stdout and stderr in a loop until an EOF message is received, or declare write attention ASTs on these mailboxes.
  • The amount of data written to SYS$OUTPUT depends on the verification status of the process (SET VERIFY/NOVERIFY command); the subprocess inherits the verification status of the parent process. It is the caller's responsibility to set the verification status of the parent process to match the expected amount of data written to SYS$OUTPUT by the subprocess.
  • Some applications, like DTM, define SYS$ERROR as SYS$OUTPUT. If stderr is not redefined by the caller, it is set in the subprocess as the parent's SYS$ERROR, which in this case translates to the parent's SYS$OUTPUT.

    If the caller redefines stdout to a pipe and does not redefine stderr , output sent to stderr goes to the pipe associated with stdout , and the amount of data written to this mailbox may be more than expected. Although redefinition of any subset of standard channels is supported, it is always safe to explicitly redefine all of them (or at least stdout and stderr ) to avoid this situation.
  • For a child process executing a DCL command procedure, SYS$COMMAND is set to the pipe specified for the child's stdin so that the parent process can feed the child requesting data from SYS$COMMAND through the pipe. For DCL command procedures, it is impossible to pass data from the parent to the child by means of the child's SYS$INPUT because for a command procedure, DCL defines SYS$INPUT as the command file itself.

Return Values

x The number of file descriptors set for the child. This number does not include file descriptors specified as - 1 in the call.
- 1 indicates that an invalid file descriptor was specified; errno is set to EBADF.

Example


 
parent.c 
======== 
 
#include <stdio.h> 
#include <string.h> 
#include <unistd.h> 
 
int decc$set_child_standard_streams(int, int, int); 
 
main() 
{ 
    int fdin[2], fdout[2], fderr[2]; 
    char msg[] = "parent writing to child's stdin"; 
    char buf[80]; 
    int nbytes; 
 
    pipe(fdin); 
    pipe(fdout); 
    pipe(fderr); 
 
    if ( vfork() == 0 ) { 
        decc$set_child_standard_streams(fdin[0], fdout[1], fderr[1]); 
      execl( "child", "child" ); 
    } 
    else { 
        write(fdin[1], msg, sizeof(msg)); 
        nbytes = read(fdout[0], buf, sizeof(buf)); 
        buf[nbytes] = '\0'; 
        puts(buf); 
        nbytes = read(fderr[0], buf, sizeof(buf)); 
        buf[nbytes] = '\0'; 
        puts(buf); 
    } 
} 
 
child.c 
======= 
 
#include <stdio.h> 
#include <unistd.h> 
 
main() 
{ 
    char msg[] = "child writing to stderr"; 
    char buf[80]; 
    int nbytes; 
 
    nbytes = read(0, buf, sizeof(buf)); 
    write(1, buf, nbytes); 
    write(2, msg, sizeof(msg)); 
} 
 
child.com 
========= 
 
$ read sys$command s 
$ write sys$output s 
$ write sys$error "child writing to stderr"

This example program returns the following for both child.c and child.com : 


$ run parent 
parent writing to child's stdin 
child writing to stderr

Note that in order to activate child.com , you must explicitly specify execl("child.com", ...) in the parent.c program.

decc$set_reentrancy

Controls the type of reentrancy that reentrant Compaq C RTL routines will exhibit.

Format

#include <reentrancy.h>

int decc$set_reentrancy (int type);

Argument

type

The type of reentrancy desired. Use one of the following values:

The reentrancy type can be raised but never lowered. The ordering of reentrancy types from low to high is C$C_NONE, C$C_TOLERANT, C$C_AST and C$C_MULTITHREAD. For example, once an application is set to multithread, a call to set the reentrancy to AST is ignored. A call to decc$set_reentrancy that attempts to lower the reentrancy type returns a value of - 1.

Description

Use the decc$set_reentrancy function to change the type of reentrancy exhibited by reentrant routines.

decc$set_reentrancy must be called exclusively at the non-AST level.

In an application using DECthreads, DECthreads automatically sets the reentrancy to multithread.

Return Value

type The type of reentrancy used before this call.
- 1 The reentrancy was set to a lower type.

decc$to_vms

Converts UNIX style file specifications to OpenVMS file specifications.

Format

#include <unixlib.h>

int decc$to_vms (const char *unix_style_filespec, int (*action_routine)(char *unix_style_filespec, int type_of_file), int allow_wild, int no_directory);

Arguments

unix_style_filespec

The address of a null-terminated string containing a name in UNIX style file specification format.

action_routine

The address of a routine that accepts the following arguments:

If action_routine returns a nonzero value (TRUE), file translation continues. If it returns a 0 value (FALSE), no further file translation takes place.

allow_wild

Either 0 or 1, passed by value. If a 0 is specified, wildcards found in unix_style_filespec are not expanded. Otherwise, wildcards are expanded and each one is passed to action_routine. Only expanded file names that correspond to existing OpenVMS files are included.

no_directory

An integer that has one of the following values:
Value Translation
0 Directory is not allowed.
1 Prevent expansion of the string as a directory name.
2 Forced to be a directory name.

Description

The decc$to_vms routine converts the given UNIX style file specification into the equivalent OpenVMS file specification (in all uppercase letters). It allows you to specify UNIX style wildcards, which are translated into a list of corresponding OpenVMS files.

Return Value

x The number of file names that result from the specified UNIX style file specification.

Example


/* Translate "UNIX" wildcard file names to VMS names    */ 
/* Define as a foreign command and provide the name     */ 
/* as an argument.                                      */ 
 
#include <unixlib.h> 
#include <stdio.h> 
int print_name(char *, int); 
int main(int argc, char *argv[]) 
{ 
    int number_found;           /* number of files found */ 
 
    printf("Translating: %s\n", argv[1]); 
 
    number_found = decc$to_vms(argv[1], print_name, 1, 0); 
    printf("%d files found\n", number_found); 
} 
 
/* action routine that prints name and type on each line */ 
 
int print_name(char *name, int type) 
{ 
    if (type == DECC$K_DIRECTORY) 
        printf("directory: %s\n", name); 
    else if (type == DECC$K_FOREIGN) 
        printf("remote non-VMS: %s\n", name); 
    else 
        printf("file:        %s\n", name); 
 
/* Translation continues as long as success status is returned */ 
    return (1); 
}

This example shows how to use the decc$to_vms routine in Compaq C. It takes a UNIX style file specification argument and displays, in OpenVMS file specification format, the name of each existing file that matches it.

decc$translate_vms

Translates OpenVMS file specifications to UNIX style file specifications.

Format

#include <unixlib.h>

char *decc$translate_vms (const char *vms_filespec);

Argument

vms_filespec

The address of a null-terminated string containing a name in OpenVMS file specification format.

Description

The decc$translate_vms function translates the given OpenVMS file specification into the equivalent UNIX style file specification, whether or not the file exists. The translated name string is stored in a thread-specific memory, which is overwritten by each call to decc$translate_vms from the same thread.

This function differs from the decc$from_vms function, which does the conversion for existing files only.

Return Values

x The address of a null-terminated string containing a name in UNIX style file specification format.
0 Indicates that the file name is null or syntactically incorrect.
- 1 Indicates that the file specification contains an ellipsis (for example, [...]a.dat), but is otherwise correct. You cannot translate the OpenVMS ellipsis syntax into a valid UNIX style file specification.

Example


/* Demonstrate translation of a "UNIX" name to VMS form */ 
/* define a foreign command and pass the name as the    */ 
/* argument.                                            */ 
            
#include <unixlib.h> 
#include <stdio.h> 
 
int main(int argc, char *argv[]) 
{ 
    char *ptr;                      /* translation result */ 
 
    ptr = decc$translate_vms( argv[1] ); 
 
    if ((int) ptr == 0 || (int) ptr == -1) 
 
        printf( "could not translate %s\n", argv[1]); 
    else 
        printf( "%s is translated to %s\n", argv[1], ptr ); 
}

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