HP OpenVMS Systems Documentation

The C RTL provides an extensive list of feature switches that can be set using DECC$ logical names. These switches affect the behavior of a C application at run time.

The feature switches introduce new behaviors and also preserve old behaviors that have been deprecated.

You enable most features by setting a logical name to ENABLE and disable a feature by setting the logical name to DISABLE:

$ DEFINE DECC$feature ENABLE

$ DEFINE DECC$feature DISABLE

Some feature logical names can be set to a numeric value. For example:

$ DEFINE DECC$PIPE_BUFFER_SIZE 32768

Table 1-5 lists the C RTL feature logical names, grouped by the type of features they control.

An alphabetic listing and description of the C RTL feature logical names follows. Unless otherwise stated, the feature logicals are enabled with ENABLE and disabled with DISABLE.

DECC$ACL_ACCESS_CHECK

The DECC$ACL_ACCESS_CHECK feature logical controls the behavior of the access function.

With DECC$ACL_ACCESS_CHECK enabled, the access function checks both UIC protection and OpenVMS Access Control Lists (ACLs).

With DECC$ACL_ACCESS_CHECK disabled, the access function checks only UIC protection.

DECC$ALLOW_REMOVE_OPEN_FILES

The DECC$ALLOW_REMOVE_OPEN_FILES feature logical controls the behavior of the remove function on open files. Ordinarily, the operation fails. However, POSIX conformance dictates that the operation succeed.

With DECC$ALLOW_REMOVE_OPEN_FILES enabled, this POSIX conformant behavior is achieved.

DECC$ALLOW_UNPRIVILEGED_NICE

With DECC$ALLOW_UNPRIVILEGED_NICE enabled, the nice function exhibits its legacy behavior of not checking the privilege of the calling process (that is, any user may lower the nice value to increase process priorities). Also, when the caller sets a priority above MAX_PRIORITY, the nice value is set to the base priority.

With DECC$ALLOW_UNPRIVILEGED_NICE disabled, the nice function conforms to the X/Open standard of checking the privilege of the calling process (only users with ALTPRI privilege can lower the nice value to increase process priorities), and when the caller sets a priority above MAX_PRIORITY, the nice value is set to MAX_PRIORITY.

DECC$ARGV_PARSE_STYLE

With DECC$ARGV_PARSE_STYLE enabled, case is preserved in command-line arguments when the process has been set up for extended DCL parsing using SET PROCESS/PARSE_STYLE=EXTENDED.

DECC$ARGV_PARSE_STYLE must be defined externally as a logical name or set in a function called using the LIB$INITIALIZE mechanism because it is evaluated before function main is called.

DECC$DEFAULT_LRL

DECC$DEFAULT_LRL specifies the default value for the RMS attribute for the longest record length. The default value 32767 is the largest record size supported by RMS.

Default: 32767

Maximum: 32767

DECC$DEFAULT_UDF_RECORD

With DECC$DEFAULT_UDF_RECORD enabled, file access mode defaults to RECORD instead of STREAM mode for all files except STREAMLF.

DECC$DETACHED_CHILD_PROCESS

With DECC$DETACHED_CHILD_PROCESS enabled, child processes created using vfork and exec are created as detached processes instead of subprocesses.

This feature has only limited support. In some cases the console cannot be shared between the parent process and the detached process, which can cause exec to fail.

DECC$DISABLE_POSIX_ROOT

With DECC$DISABLE_POSIX_ROOT enabled, support for the POSIX root directory defined by SYS$POSIX_ROOT is disabled.

With DECC$DISABLE_POSIX_ROOT disabled, the SYS$POSIX_ROOT logical name is interpreted as the equivalent of the file path "/". If a UNIX path starting with a slash (/) is given and the value after the leading slash cannot be translated as a logical name, SYS$POSIX_ROOT is used as the parent directory for the specified UNIX file path.

The C RTL supports a UNIX style root that behaves like a real directory. This allows such actions as:

% cd / % mkdir /dirname % tar -xvf tarfile.tar /dirname % ls /

Previously, the C RTL did not recognize "/" as a directory name. The normal processing for a file path starting with "/" was to interpret the first element as a logical name or device name. If this failed, there was special processing for the name /dev/null and names starting with /bin and /tmp :

/dev/null NLA0: /bin SYS$SYSTEM: /tmp SYS$SCRATCH:

These behaviors are retained for compatibility purposes. In addition, support has been added to the C RTL for the logical name SYS$POSIX_ROOT as an equivalent to "/".

To enable this feature for use by the C RTL, define SYS$POSIX_ROOT as a concealed logical name. For example:

$ DEFINE/TRANSLATION=(CONCEALED,TERMINAL) SYS$POSIX_ROOT "$1$DKA0:[SYS0.abc.]"

To disable this feature:

$ DEFINE DECC$DISABLE_POSIX_ROOT DISABLE

Enabling SYS$POSIX_ROOT results in the following behavior:

• If the existing translation of a UNIX path starting with "/" fails and SYS$POSIX_ROOT is defined, the name is interpreted as if it starts with /sys$posix_root .
• When converting from an OpenVMS to a UNIX style file name, and the OpenVMS name starts with "SYS$POSIX_ROOT:", then the "SYS$POSIX_ROOT:" is removed. For example, SYS$POSIX_ROOT:[dirname] becomes /dirname . If the resulting name could be interpreted as a logical name or one of the special cases previously listed, the result is /./dirname instead of /dirname .

DECC$DISABLE_TO_VMS_LOGNAME_TRANSLATION

With DECC$DISABLE_TO_VMS_LOGNAME_TRANSLATION enabled, the conversion routine decc$to_vms will only treat the first element of a UNIX style name as a logical name if there is a leading slash (/).

DECC$EFS_CASE_PRESERVE

With DECC$EFS_CASE_PRESERVE enabled, case is preserved for file names on ODS-5 disks.

With DECC$EFS_CASE_PRESERVE disabled, UNIX style file names are always reported in lowercase.

However, note that enabling DECC$EFS_CASE_SPECIAL overrides the setting for DECC$EFS_CASE_PRESERVE.

DECC$EFS_CASE_SPECIAL

With DECC$EFS_CASE_SPECIAL enabled, case is preserved only for file names containing lowercase. If an element of a file name contains all uppercase letters, it is reported in all lowercase in UNIX style.

When enabled, DECC$EFS_CASE_SPECIAL overrides the value of DECC$EFS_CASE_PRESERVE.

DECC$EFS_CHARSET

With DECC$EFS_CHARSET enabled, UNIX names can contain ODS-5 extended characters. Support includes multiple dots and all ASCII characters in the range 0 to 255, except the following:

<NUL>
/
"
*
?

Unless DECC$FILENAME_UNIX_ONLY is enabled, some characters can be interpreted as OpenVMS characters depending on context. They are:

:
[
<
^
;

DECC$EFS_CHARSET might be necessary for existing applications that make assumptions about file names based on the presence of certain characters, because the following nonstandard and undocumented C RTL extensions do not work when EFS extended character-set support is enabled:

• $HOME is interpreted as the user's login directory
  With DECC$EFS_CHARSET enabled, $HOME is treated literally and may be in an OpenVMS or UNIX style file name.
• ~name is interpreted as the login directory for user name
  With DECC$EFS_CHARSET enabled, ~name is treated literally and can be in an OpenVMS or UNIX style file name.
• Wild card regular expressions in the form [a-z]
  With DECC$EFS_CHARSET enabled, square brackets are acceptable in OpenVMS and UNIX style file names. For instance, in a function such as open , abc[a-z]ef.txt is interpreted as a UNIX style name equivalent to the OpenVMS style name abc^[a-z^]ef.txt , and [a-z]bc is interpreted as an OpenVMS style name equivalent to the UNIX style name /sys$disk/a-z/bc .

With DECC$EFS_CHARSET enabled, the following encoding for EFS extended characters is supported when converting from an OpenVMS style file name to a UNIX style file name:

• All ODS-2 compatible names
• All encoding for 8-bit characters, either as single byte or using two-digit hexadecimal form ^ab . In a UNIX path these are always represented as a single byte.
• Encoding for DEL (^7F)
• The following characters when preceded by a caret:

  space ! , _ & ' ( ) + @ { } ; # [ ] % ^ = $ - ~ .

• The following characters when not preceded by a caret:

  $ - ~ .

• The implementation supports the conversion from OpenVMS to UNIX needed for functions readdir , ftw , getname , fgetname , getcwd , and others.

DECC$EFS_FILE_TIMESTAMPS

With DECC$EFS_FILE_TIMESTAMPS enabled, stat and fstat report new ODS-5 access time ( st_atime ), attribute revision time ( st_ctime ) and modification time ( st_mtime ) for files on ODS-5 volumes that have the extended file times enabled using SET VOLUME/VOLUME=ACCESS_DATES.

If DECC$EFS_FILE_TIMESTAMPS is disabled, or the volume is not ODS-5, or the volume does not have support for these additional times enabled, st_ctime continues to be the file creation time and st_atime the same as the st_mtime .

The utime and utimes functions support these ODS-5 times in the same way as stat .

DECC$EFS_NO_DOTS_IN_DIRNAME

With support for extended characters in file names for ODS-5, a name such as NAME.EXT can be interpreted as NAME.EXT.DIR. Determining if directory [.name^.ext] exists adds overhead to UNIX name translation when support for extended character support in UNIX file names is enabled.

Enabling the DECC$EFS_NO_DOTS_IN_DIRNAME feature logical suppresses the interpretation of a file name containing dots as a directory name. With this logical enabled, NAME.EXT is assumed to be a file name; no check is made for directory [.name^.ext].

DECC$ENABLE_GETENV_CACHE

The C RTL supplements the list of environment variables in the environ table with all logical names and DCL symbols available to the process.

By default, whenever getenv is called for a name not in the environ table, an attempt is made to resolve this as a logical name and, if this fails, as a DCL symbol.

With DECC$ENABLE_GETENV_CACHE enabled, once a logical name or DCL name has been successfully translated, its value is stored in a cache. When the same name is requested in a future call to getenv , the value is returned from the cache instead of reevaluating the logical name or DCL symbol.

DECC$ENABLE_TO_VMS_LOGNAME_CACHE

Use the DECC$ENABLE_TO_VMS_LOGNAME_CACHE to improve the performance of UNIX name translation. The value is the life of each cache entry in seconds. The equivalence string ENABLE is evaluated as 1 second.

Define DECC$ENABLE_TO_VMS_LOGNAME_CACHE to 1 to enable the cache with a 1-second life for each entry.

Define DECC$ENABLE_TO_VMS_LOGNAME_CACHE to 2 to enable the cache with a 2-second life for each entry.

Define DECC$ENABLE_TO_VMS_LOGNAME_CACHE to - 1 to enable the cache without a cache entry expiration.

DECC$EXEC_FILEATTR_INHERITANCE

The DECC$EXEC_FILEATTR_INHERITANCE feature logical affects child processes that are C programs.

For versions of OpenVMS before Version 7.3-2, DECC$EXEC_FILEATTR_INHERITANCE is either enabled or disabled:

• With DECC$EXEC_FILEATTR_INHERITANCE enabled, the current file pointer and the file open mode is passed to the child process in exec calls.
• With this logical name disabled, the child process does not inherit append mode or the file position.

For OpenVMS Version 7.3-2 and higher, DECC$EXEC_FILEATTR_INHERITANCE can be defined to 1 or 2, or be disabled:

• With DECC$EXEC_FILEATTR_INHERITANCE defined to 1, a child process inherits file positioning for all file access modes except append.
• With DECC$EXEC_FILEATTR_INHERITANCE defined to 2, a child process inherits file positioning for all file access modes including append.
• With DECC$EXEC_FILEATTR_INHERITANCE disabled, a child process does not inherit the file position for any access modes.

DECC$FILENAME_UNIX_ONLY

With DECC$FILENAME_UNIX_ONLY enabled, file names are never interpreted as OpenVMS style names. This prevents any interpretation of the following as OpenVMS special characters:

: [ ^

DECC$FILENAME_UNIX_NO_VERSION

With DECC$FILENAME_UNIX_NO_VERSION enabled, OpenVMS version numbers are not supported in UNIX style file names.

With DECC$FILENAME_UNIX_NO_VERSION disabled, in UNIX style names, version numbers are reported preceded by a period (.).

DECC$FILENAME_UNIX_REPORT

With DECC$FILENAME_UNIX_REPORT enabled, all file names are reported in UNIX style unless the caller specifically selects OpenVMS style. This applies to getpwnam , getpwuid , argv[0] , getname , fgetname , and tempnam .

With DECC$FILENAME_UNIX_REPORT disabled, unless specified in the function call, file names are reported in OpenVMS style.

DECC$FILE_PERMISSION_UNIX

With DECC$FILE_PERMISSION_UNIX enabled, the file permissions for new files and directories are set according to the file creation mode and umask . This includes mode 0777. When an earlier version of the file exists, the file permissions for the new file are inherited from the earlier version. This mode sets DELETE permission for a new directory when WRITE permission is enabled.

With DECC$FILE_PERMISSION_UNIX disabled, modes 0 and 0777 indicate using RMS default protection or protection from the previous version of the file. Permissions for new directories also follow OpenVMS rules, including disabling DELETE permissions.

DECC$FILE_SHARING

With DECC$FILE_SHARING enabled, all files are opened with full sharing enabled (FAB$M_DEL | FAB$M_GET | FAB$M_PUT | FAB$M_UPD). This is set as a logical OR with any sharing mode specified by the caller.

DECC$FIXED_LENGTH_SEEK_TO_EOF

With DECC$FIXED_LENGTH_SEEK_TO_EOF enabled, lseek , fseeko , and fseek with the direction paremeter set to SEEK_END will position relative to the last byte in the file for files with fixed-length records.

With DECC$FIXED_LENGTH_SEEK_TO_EOF disabled, lseek , fseek , and fseeko when called with SEEK_EOF on files with fixed-length records, will position relative to the end of the last record in the file.

DECC$GLOB_UNIX_STYLE

Enabling DECC$GLOB_UNIX_STYLE selects the UNIX mode of the glob function.

DECC$LOCALE_CACHE_SIZE

DECC$LOCALE_CACHE_SIZE defines how much memory, in bytes, to allocate for caching locale data. The default value is 0, which disables the locale cache.

Default: 0

Maximum: 2147483647

DECC$MAILBOX_CTX_STM

By default, an open on a local mailbox that is not a pipe treats mailbox records as having a record attribute of FAB$M_CR.

With DECC$MAILBOX_CTX_STM enabled, the record attribute FAB$M_CR is not set.

DECC$NO_ROOTED_SEARCH_LISTS

When the decc$to_vms function evaluates a UNIX style path string, if it determines the first element to be a logical name, then:

• For rooted logicals or devices, it appends ":[000000]" to the logical name.
  For example, if log1 is a rooted logical ($DEFINE LOG1 [DIR_NAME.]) then /log1/filename.ext translates to LOG1:[000000]FILENAME.EXT.
• For nonrooted logicals, it appends just a colon (:) to the logical name.
  For example, if log2 is a nonrooted logical ($ DEFINE LOG2 [DIR_NAME]), then /log2/filename.ext translates to LOG2:FILENAME.EXT.
• If the first element is a search-list logical, the translation proceeds by evaluating the first element in the search list, and translating the path as previously described.

The preceding three cases lead to predictable, expected results.

In the case where the first element is a search list that consists of a mixture of rooted and nonrooted logicals, translating paths as described previously can lead to different behavior from that of older versions of OpenVMS (before OpenVMS Version 7.3-1):

• Before OpenVMS Version 7.3-1, regardless of the contents of the logical, the decc$to_vms function appended only a colon (:). For search lists that consisted of a mixture of rooted and nonrooted logicals, this resulted in certain expected behaviors.
• For OpenVMS Version 7.3-1 and later, if the first element of the mixed search list is a rooted logical, then decc$to_vms appends ":[000000]" to the logical name, resulting in different behavior from that of OpenVMS releases prior to Version 7.3-1.

DECC$NO_ROOTED_SEARCH_LISTS controls how the decc$to_vms function resolves search-list logicals and provides a means to restore the OpenVMS behavior prior to Version 7.3-1.

---

Previous

Next

Contents

Index