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       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       delta — make a delta (change) to an SCCS file (DEVELOPMENT)

SYNOPSIS

       delta [-nps] [-g list] [-m mrlist] [-r SID] [-y[comment]] file...

DESCRIPTION

       The delta utility shall be used to permanently introduce into the named SCCS files changes
       that were made to the files retrieved by get (called the g-files, or generated files).

OPTIONS

The delta utility shall conform to the Base Definitions volume of POSIX.1‐2017, Section
12.2, Utility Syntax Guidelines, except that the -y option has an optional option-
argument. This optional option-argument shall not be presented as a separate argument.

The following options shall be supported:

-r SID Uniquely identify which delta is to be made to the SCCS file. The use of this
option shall be necessary only if two or more outstanding get commands for
editing (get -e) on the same SCCS file were done by the same person (login
name). The SID value specified with the -r option can be either the SID
specified on the get command line or the SID to be made as reported by the get
utility; see get.

-s Suppress the report to standard output of the activity associated with each
file. See the STDOUT section.

-n Specify retention of the edited g-file (normally removed at completion of delta
processing).

-g list Specify a list (see get for the definition of list) of deltas that shall be
ignored when the file is accessed at the change level (SID) created by this
delta.

-m mrlist Specify a modification request (MR) number that the application shall supply as
the reason for creating the new delta. This shall be used if the SCCS file has
the v flag set; see admin.

If -m is not used and '-' is not specified as a file argument, and the standard
input is a terminal, the prompt described in the STDOUT section shall be written
to standard output before the standard input is read; if the standard input is
not a terminal, no prompt shall be issued.

MRs in a list shall be separated by <blank> characters or escaped <newline>
characters. An unescaped <newline> shall terminate the MR list. The escape
character is <backslash>.

If the v flag has a value, it shall be taken to be the name of a program which
validates the correctness of the MR numbers. If a non-zero exit status is
returned from the MR number validation program, the delta utility shall
terminate. (It is assumed that the MR numbers were not all valid.)

-y[comment]
Describe the reason for making the delta. The comment shall be an arbitrary
group of lines that would meet the definition of a text file. Implementations
shall support comments from zero to 512 bytes and may support longer values. A
null string (specified as either -y, -y"", or in response to a prompt for a
comment) shall be considered a valid comment.

If -y is not specified and '-' is not specified as a file argument, and the
standard input is a terminal, the prompt described in the STDOUT section shall
be written to standard output before the standard input is read; if the standard
input is not a terminal, no prompt shall be issued. An unescaped <newline> shall
terminate the comment text. The escape character is <backslash>.

The -y option shall be required if the file operand is specified as '-'.

-p Write (to standard output) the SCCS file differences before and after the delta
is applied in diff format; see diff.

OPERANDS

       The following operand shall be supported:

       file      A pathname of an existing SCCS file or a directory. If file is a directory,  the
                 delta  utility  shall behave as though each file in the directory were specified
                 as a named file, except that non-SCCS files (last component of the pathname does
                 not begin with s.)  and unreadable files shall be silently ignored.

                 If  exactly one file operand appears, and it is '-', the standard input shall be
                 read; each line of the standard input shall be taken to be the name of  an  SCCS
                 file  to  be  processed.  Non-SCCS  files and unreadable files shall be silently
                 ignored.

STDIN

       The standard input shall be a text file used only in the following cases:

        *  To read an mrlist or a comment (see the -m and -y options).

        *  A file operand shall be specified as '-'.  In this case, the -y option must be used to
           specify  the comment, and if the SCCS file has the v flag set, the -m option must also
           be used to specify the MR list.

INPUT FILES

       Input files shall be text files whose data is to be included in the  SCCS  files.  If  the
       first character of any line of an input file is <SOH> in the POSIX locale, the results are
       unspecified. If this file contains more than 99999 lines, the number of lines recorded  in
       the header for this file shall be 99999 for this delta.

ENVIRONMENT VARIABLES

       The following environment variables shall affect the execution of delta:

       LANG      Provide a default value for the internationalization variables that are unset or
                 null.  (See  the  Base  Definitions  volume  of   POSIX.1‐2017,   Section   8.2,
                 Internationalization   Variables  for  the  precedence  of  internationalization
                 variables used to determine the values of locale categories.)

       LC_ALL    If set to a non-empty string  value,  override  the  values  of  all  the  other
                 internationalization variables.

       LC_CTYPE  Determine  the  locale for the interpretation of sequences of bytes of text data
                 as characters (for example, single-byte as opposed to multi-byte  characters  in
                 arguments and input files).

       LC_MESSAGES
                 Determine  the  locale  that should be used to affect the format and contents of
                 diagnostic messages written to standard error, and informative messages  written
                 to standard output.

       NLSPATH   Determine the location of message catalogs for the processing of LC_MESSAGES.

       TZ        Determine  the timezone in which the time and date are written in the SCCS file.
                 If the TZ variable is unset or NULL, an unspecified system default  timezone  is
                 used.

ASYNCHRONOUS EVENTS

       If  SIGINT is caught, temporary files shall be cleaned up and delta shall exit with a non-
       zero exit code. The standard action shall be taken for all other signals; see Section 1.4,
       Utility Description Defaults.

STDOUT

       The standard output shall be used only for the following messages in the POSIX locale:

        *  Prompts (see the -m and -y options) in the following formats:

               "MRs? "

               "comments? "

           The MR prompt, if written, shall always precede the comments prompt.

        *  A  report  of  each  file's  activities  (unless  the  -s  option is specified) in the
           following format:

               "%s\n%d inserted\n%d deleted\n%d unchanged\n", <New SID>,
                   <number of lines inserted>, <number of lines deleted>,
                   <number of lines unchanged>

STDERR

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES

       Any SCCS files updated shall be files of an unspecified format.

EXTENDED DESCRIPTION

   System Date and Time
       When a delta is added to an SCCS file, the system date and time shall be recorded for  the
       new delta. If a get is performed using an SCCS file with a date recorded apparently in the
       future, the behavior is unspecified.

EXIT STATUS

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

       Problems can arise if the system date and  time  have  been  modified  (for  example,  put
       forward and then back again, or unsynchronized clocks across a network) and can also arise
       when different values of the TZ environment variable are used.

       Problems of a similar nature can also arise for the operation of the  get  utility,  which
       records the date and time in the file body.

EXAMPLES

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

COPYRIGHT

       Portions of this text are reprinted and  reproduced  in  electronic  form  from  IEEE  Std
       1003.1-2017,  Standard  for  Information Technology -- Portable Operating System Interface
       (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C)  2018  by
       the  Institute  of  Electrical  and Electronics Engineers, Inc and The Open Group.  In the
       event of any discrepancy between this version and the original IEEE  and  The  Open  Group
       Standard,  the  original  IEEE  and  The  Open Group Standard is the referee document. The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are most  likely  to  have
       been  introduced  during  the conversion of the source files to man page format. To report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .