DELTA(1P)

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.

SEE ALSO
Section 1.4, Utility Description Defaults, admin, diff, get, prs, rmdel

The Base Definitions volume of POSIX.1-2017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines

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 .

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