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PROLOG

       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 .

IEEE/The Open Group                                   2017                                         DELTA(1POSIX)