-@node Data Input and Output, System and Portable Files, Expressions, Top
+@node Data Input and Output
@chapter Data Input and Output
@cindex input
@cindex output
pertaining to single respondent is a case.
This chapter examines
the PSPP commands for defining variables and reading and writing data.
+There are alternative commands to read data from predefined sources
+such as system files or databases (@xref{GET, GET DATA}.)
@quotation Note
These commands tell PSPP how to read data, but the data will not
@menu
* BEGIN DATA:: Embed data within a syntax file.
-* CLEAR TRANSFORMATIONS:: Clear pending transformations.
* CLOSE FILE HANDLE:: Close a file handle.
+* DATAFILE ATTRIBUTE:: Set custom attributes on data files.
* DATA LIST:: Fundamental data reading command.
* END CASE:: Output the current case.
* END FILE:: Terminate the current input program.
END DATA.
@end example
-@node CLEAR TRANSFORMATIONS
-@section CLEAR TRANSFORMATIONS
-@vindex CLEAR TRANSFORMATIONS
-
-@display
-CLEAR TRANSFORMATIONS.
-@end display
-
-@cmd{CLEAR TRANSFORMATIONS} clears out all pending
-transformations. It does not cancel the current input program.
-
@node CLOSE FILE HANDLE
@section CLOSE FILE HANDLE
@cmd{CLOSE FILE HANDLE} is a PSPP extension.
+@node DATAFILE ATTRIBUTE
+@section DATAFILE ATTRIBUTE
+@vindex DATAFILE ATTRIBUTE
+
+@display
+DATAFILE ATTRIBUTE
+ ATTRIBUTE=name('value') [name('value')]@dots{}
+ ATTRIBUTE=name@b{[}index@b{]}('value') [name@b{[}index@b{]}('value')]@dots{}
+ DELETE=name [name]@dots{}
+ DELETE=name@b{[}index@b{]} [name@b{[}index@b{]}]@dots{}
+@end display
+
+@cmd{DATAFILE ATTRIBUTE} adds, modifies, or removes user-defined
+attributes associated with the active file. Custom data file
+attributes are not interpreted by PSPP, but they are saved as part of
+system files and may be used by other software that reads them.
+
+Use the ATTRIBUTE subcommand to add or modify a custom data file
+attribute. Specify the name of the attribute as an identifier
+(@pxref{Tokens}), followed by the desired value, in parentheses, as a
+quoted string. Attribute names that begin with @code{$} are reserved
+for PSPP's internal use, and attribute names that begin with @code{@@}
+or @code{$@@} are not displayed by most PSPP commands that display
+other attributes. Other attribute names are not treated specially.
+
+Attributes may also be organized into arrays. To assign to an array
+element, add an integer array index enclosed in square brackets
+(@code{[} and @code{]}) between the attribute name and value. Array
+indexes start at 1, not 0. An attribute array that has a single
+element (number 1) is not distinguished from a non-array attribute.
+
+Use the DELETE subcommand to delete an attribute. Specify an
+attribute name by itself to delete an entire attribute, including all
+array elements for attribute arrays. Specify an attribute name
+followed by an array index in square brackets to delete a single
+element of an attribute array. In the latter case, all the array
+elements numbered higher than the deleted element are shifted down,
+filling the vacated position.
+
+To associate custom attributes with particular variables, instead of
+with the entire active file, use @cmd{VARIABLE ATTRIBUTE} (@pxref{VARIABLE ATTRIBUTE}) instead.
+
+@cmd{DATAFILE ATTRIBUTE} takes effect immediately. It is not affected
+by conditional and looping structures such as @cmd{DO IF} or
+@cmd{LOOP}.
+
@node DATA LIST
@section DATA LIST
@vindex DATA LIST
Each form of @cmd{DATA LIST} is described in detail below.
+@xref{GET DATA}, for a command that offers a few enhancements over
+DATA LIST and that may be substituted for DATA LIST in many
+situations.
+
@menu
* DATA LIST FIXED:: Fixed columnar locations for data.
* DATA LIST FREE:: Any spacing you like.
@display
DATA LIST [FIXED]
@{TABLE,NOTABLE@}
- [FILE='file-name']
+ [FILE='file-name' [ENCODING='encoding']]
[RECORDS=record_count]
[END=end_var]
[SKIP=record_count]
file handle (@pxref{File Handles}). If the FILE subcommand is not used,
then input is assumed to be specified within the command file using
@cmd{BEGIN DATA}@dots{}@cmd{END DATA} (@pxref{BEGIN DATA}).
+The ENCODING subcommand may only be used if the FILE subcommand is also used.
+It specifies the character encoding of the file.
The optional RECORDS subcommand, which takes a single integer as an
argument, is used to specify the number of lines per record. If RECORDS
@itemize @bullet
@item
-@code{NAME}, a 10-character-wide long string variable, in columns 1
+@code{NAME}, a 10-character-wide string variable, in columns 1
through 10.
@item
@code{ID}, a numeric variable, in columns 1-5 of the first record.
@item
-@code{NAME}, a 30-character long string variable, in columns 7-36 of the
+@code{NAME}, a 30-character string variable, in columns 7-36 of the
first record.
@item
-@code{SURNAME}, a 30-character long string variable, in columns 38-67 of
+@code{SURNAME}, a 30-character string variable, in columns 38-67 of
the first record.
@item
-@code{MINITIAL}, a 1-character short string variable, in column 69 of
+@code{MINITIAL}, a 1-character string variable, in column 69 of
the first record.
@item
DATA LIST FREE
[(@{TAB,'c'@}, @dots{})]
[@{NOTABLE,TABLE@}]
- [FILE='file-name']
- [END=end_var]
+ [FILE='file-name' [ENCODING='encoding']]
[SKIP=record_cnt]
/var_spec@dots{}
The NOTABLE and TABLE subcommands are as in @cmd{DATA LIST FIXED} above.
NOTABLE is the default.
-The FILE, END, and SKIP subcommands are as in @cmd{DATA LIST FIXED} above.
+The FILE and SKIP subcommands are as in @cmd{DATA LIST FIXED} above.
The variables to be parsed are given as a single list of variable names.
This list must be introduced by a single slash (@samp{/}). The set of
DATA LIST LIST
[(@{TAB,'c'@}, @dots{})]
[@{NOTABLE,TABLE@}]
- [FILE='file-name']
- [END=end_var]
+ [FILE='file-name' [ENCODING='encoding']]
[SKIP=record_count]
/var_spec@dots{}
[/MODE=CHARACTER]
/TABWIDTH=tab_width
-For binary files with fixed-length records:
+For binary files in native encoding with fixed-length records:
FILE HANDLE handle_name
/NAME='file-name'
/MODE=IMAGE
[/LRECL=rec_len]
+For binary files in native encoding with variable-length records:
+ FILE HANDLE handle_name
+ /NAME='file-name'
+ /MODE=BINARY
+ [/LRECL=rec_len]
+
+For binary files encoded in EBCDIC:
+ FILE HANDLE handle_name
+ /NAME='file-name'
+ /MODE=360
+ /RECFORM=@{FIXED,VARIABLE,SPANNED@}
+ [/LRECL=rec_len]
+
To explicitly declare a scratch handle:
FILE HANDLE handle_name
/MODE=SCRATCH
invocation of @cmd{FILE HANDLE}, unless it has been closed by an
intervening command (@pxref{CLOSE FILE HANDLE}).
-MODE specifies a file mode. In CHARACTER mode, the default, the data
-file is read as a text file, according to the local system's
-conventions, and each text line is read as one record.
-In CHARACTER mode, most input programs will expand tabs to spaces
-(@cmd{DATA LIST FREE} with explicitly specified delimiters is an
-exception). By default, each tab is 4 characters wide, but an
-alternate width may be specified on TABWIDTH. A tab width of 0
-suppresses tab expansion entirely.
-
-In IMAGE mode, the data file is opened in ANSI C binary mode. Record
-length is fixed, with output data truncated or padded with spaces to
-the record length. LRECL specifies the record length in bytes, with a
-default of 1024. Tab characters are never expanded to spaces in
-binary mode. Records
+The effect and syntax of FILE HANDLE depends on the selected MODE:
-The NAME subcommand specifies the name of the file associated with the
-handle. It is required in CHARACTER and IMAGE modes.
+@itemize
+@item
+In CHARACTER mode, the default, the data file is read as a text file,
+according to the local system's conventions, and each text line is
+read as one record.
+
+In CHARACTER mode only, tabs are expanded to spaces by input programs,
+except by @cmd{DATA LIST FREE} with explicitly specified delimiters.
+Each tab is 4 characters wide by default, but TABWIDTH (a PSPP
+extension) may be used to specify an alternate width. Use a TABWIDTH
+of 0 to suppress tab expansion.
+
+@item
+In IMAGE mode, the data file is treated as a series of fixed-length
+binary records. LRECL should be used to specify the record length in
+bytes, with a default of 1024. On input, it is an error if an IMAGE
+file's length is not a integer multiple of the record length. On
+output, each record is padded with spaces or truncated, if necessary,
+to make it exactly the correct length.
+
+@item
+In BINARY mode, the data file is treated as a series of
+variable-length binary records. LRECL may be specified, but its value
+is ignored. The data for each record is both preceded and followed by
+a 32-bit signed integer in little-endian byte order that specifies the
+length of the record. (This redundancy permits records in these
+files to be efficiently read in reverse order, although PSPP always
+reads them in forward order.) The length does not include either
+integer.
+
+@item
+Mode 360 reads and writes files in formats first used for tapes in the
+1960s on IBM mainframe operating systems and still supported today by
+the modern successors of those operating systems. For more
+information, see @cite{OS/400 Tape and Diskette Device Programming},
+available on IBM's website.
-The SCRATCH mode designates the file handle as a scratch file handle.
+Alphanumeric data in mode 360 files are encoded in EBCDIC. PSPP
+translates EBCDIC to or from the host's native format as necessary on
+input or output, using an ASCII/EBCDIC translation that is one-to-one,
+so that a ``round trip'' from ASCII to EBCDIC back to ASCII, or vice
+versa, always yields exactly the original data.
+
+The RECFORM subcommand is required in mode 360. The precise file
+format depends on its setting:
+
+@table @asis
+@item F
+@itemx FIXED
+This record format is equivalent to IMAGE mode, except for EBCDIC
+translation.
+
+IBM documentation calls this @code{*F} (fixed-length, deblocked)
+format.
+
+@item V
+@itemx VARIABLE
+The file comprises a sequence of zero or more variable-length blocks.
+Each block begins with a 4-byte @dfn{block descriptor word} (BDW).
+The first two bytes of the BDW are an unsigned integer in big-endian
+byte order that specifies the length of the block, including the BDW
+itself. The other two bytes of the BDW are ignored on input and
+written as zeros on output.
+
+Following the BDW, the remainder of each block is a sequence of one or
+more variable-length records, each of which in turn begins with a
+4-byte @dfn{record descriptor word} (RDW) that has the same format as
+the BDW. Following the RDW, the remainder of each record is the
+record data.
+
+The maximum length of a record in VARIABLE mode is 65,527 bytes:
+65,535 bytes (the maximum value of a 16-bit unsigned integer), minus 4
+bytes for the BDW, minus 4 bytes for the RDW.
+
+In mode VARIABLE, LRECL specifies a maximum, not a fixed, record
+length, in bytes. The default is 8,192.
+
+IBM documentation calls this @code{*VB} (variable-length, blocked,
+unspanned) format.
+
+@item VS
+@itemx SPANNED
+The file format is like that of VARIABLE mode, except that logical
+records may be split among multiple physical records (called
+@dfn{segments}) or blocks. In SPANNED mode, the third byte of each
+RDW is called the segment control character (SCC). Odd SCC values
+cause the segment to be appended to a record buffer maintained in
+memory; even values also append the segment and then flush its
+contents to the input procedure. Canonically, SCC value 0 designates
+a record not spanned among multiple segments, and values 1 through 3
+designate the first segment, the last segment, or an intermediate
+segment, respectively, within a multi-segment record. The record
+buffer is also flushed at end of file regardless of the final record's
+SCC.
+
+The maximum length of a logical record in VARIABLE mode is limited
+only by memory available to PSPP. Segments are limited to 65,527
+bytes, as in VARIABLE mode.
+
+This format is similar to what IBM documentation call @code{*VS}
+(variable-length, deblocked, spanned) format.
+@end table
+
+In mode 360, fields of type A that extend beyond the end of a record
+read from disk are padded with spaces in the host's native character
+set, which are then translated from EBCDIC to the native character
+set. Thus, when the host's native character set is based on ASCII,
+these fields are effectively padded with character @code{X'80'}. This
+wart is implemented for compatibility.
+
+@item
+SCRATCH mode is a PSPP extension that designates the file handle as a
+scratch file handle.
Its use is usually unnecessary because file handle names that begin with
@samp{#} are assumed to refer to scratch files. @pxref{File Handles},
for more information.
+@end itemize
+
+The NAME subcommand specifies the name of the file associated with the
+handle. It is required in all modes but SCRATCH mode, in which its
+use is forbidden.
@node INPUT PROGRAM
@section INPUT PROGRAM
All this is very confusing. A few examples should help to clarify.
+@c If you change this example, change the regression test1 in
+@c tests/command/input-program.sh to match.
@example
INPUT PROGRAM.
DATA LIST NOTABLE FILE='a.data'/X 1-10.
Y from file @file{b.data}. If one file is shorter than the other then
the extra data in the longer file is ignored.
+@c If you change this example, change the regression test2 in
+@c tests/command/input-program.sh to match.
@example
INPUT PROGRAM.
NUMERIC #A #B.
field is set to the system-missing value alongside the present value for
the remaining length of the longer file.
+@c If you change this example, change the regression test3 in
+@c tests/command/input-program.sh to match.
@example
INPUT PROGRAM.
NUMERIC #A #B.
The above example reads data from file @file{a.data}, then from
@file{b.data}, and concatenates them into a single active file.
+@c If you change this example, change the regression test4 in
+@c tests/command/input-program.sh to match.
@example
INPUT PROGRAM.
NUMERIC #EOF.
The above example does the same thing as the previous example, in a
different way.
+@c If you change this example, make similar changes to the regression
+@c test5 in tests/command/input-program.sh.
@example
INPUT PROGRAM.
LOOP #I=1 TO 50.
system-missing value as a field filled with spaces. Binary formats
are an exception.
@end itemize
-@setfilename ignored
projects / pspp-builds.git / blobdiff