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1.1 root 1: .\" Copyright (c) 1980 Regents of the University of California.
2: .\" All rights reserved. The Berkeley software License Agreement
3: .\" specifies the terms and conditions for redistribution.
4: .\"
5: .\" @(#)f77IO.ms 5.4 (Berkeley) 4/28/86
6: .\"
7: .EH 'PS1:3-%''Introduction to the f77 I/O Library'
8: .OH 'Introduction to the f77 I/O Library''PS1:3-%'
9: .de Fo
10: Fortran\\$1
11: ..
12: .de Sm
13: \s-1\\$1\s0
14: ..
15: .\"
16: .\" Nh macro - same as NH but also saves heading for table of contents
17: .\" Nh usage: Nh level string, e.g.: .Nh 2 "Calculator Sample"
18: .de Nh
19: .NH \\$1
20: \\$2
21: .XS
22: .if '2'\\$1' .ti .25i
23: .if '3'\\$1' .ti .5i
24: \\*(SN \\$2
25: .XE
26: .PP
27: ..
28: .ND ""
29: .\" .nr ll 7.0i
30: .\" .nr LL 7.0i
31: .\" .po 0.0i
32: .\" .rm PT
33: .\" .rm BT
34: .\".RP
35: .TL
36: Introduction to the f77 I/O Library
37: .AU
38: David L. Wasley
39: .AU
40: J. Berkman
41: .AI
42: University of California, Berkeley
43: Berkeley, California 94720
44: .AB
45: The f77 I/O library, libI77.a,
46: includes routines to perform all of the standard types of
47: .Fo
48: input and output specified in the
49: .Sm ANSI
50: 1978
51: .Fo
52: standard.
53: The I/O Library was written originally by Peter J. Weinberger at Bell Labs.
54: Where the original implementation was incomplete,
55: it has been rewritten to more closely implement the standard.
56: Where the standard is vague,
57: we have tried to provide flexibility within the constraints of the
58: .UX
59: operating system.
60: A number of logical extensions and enhancements have been provided
61: such as the use of the C stdio library routines to provide
62: efficient buffering for file I/O.
63: .sp 2
64: .LP
65: Revised September, 1985
66: .AE
67: .LP
68: .\" page 2 is allocated to the table of contents
69: .pn 3
70: .bp
71: .Nh 1 "Fortran I/O"
72: The requirements of the
73: .Sm ANSI
74: standard impose significant overhead
75: on programs that do large amounts of I/O. Formatted I/O can be
76: very ``expensive'' while direct access binary I/O is usually very efficient.
77: Because of the complexity of
78: .Fo
79: I/O,
80: some general concepts deserve clarification.
81: .Nh 2 "Types of I/O and logical records"
82: There are four forms of I/O:
83: .B formatted,
84: .B unformatted,
85: .B list\ directed,
86: and
87: .B namelist.
88: The last two are
89: related to formatted but do not obey all the rules for formatted I/O.
90: There are two types of ``files'':
91: .B external
92: and
93: .B internal
94: and two modes of access to files:
95: .B direct
96: and
97: .B sequential.
98: The definition of a logical record depends upon the
99: combination of I/O form, file type, and access mode specified by the
100: .Fo
101: I/O statement.
102: .Nh 3 "Direct access external I/O"
103: A logical record in a
104: .B direct
105: access
106: .B external
107: file is a string of bytes
108: of a length specified when the file is opened.
109: Read and write statements must not specify logical records longer than
110: the original record size definition. Shorter logical records are allowed.
111: .B Unformatted
112: direct writes leave the unfilled part of the record undefined.
113: .B Formatted
114: direct writes cause the unfilled record to be padded with blanks.
115: .Nh 3 "Sequential access external I/O"
116: Logical records in
117: .B sequentially
118: accessed
119: .B external
120: files may be of arbitrary
121: and variable length.
122: Logical record length for
123: .B unformatted
124: sequential files is determined by
125: the size of items in the iolist.
126: The requirements of this form of I/O cause the external physical
127: record size to be somewhat larger than the logical record size.
128: For
129: .B formatted
130: write statements, logical record length is determined by
131: the format statement interacting with the iolist at execution time.
132: The ``newline'' character is the logical record delimiter.
133: Formatted sequential access causes one or more logical records
134: ending with ``newline'' characters to be read or written.
135: .Nh 3 "List directed and namelist sequential external I/O"
136: Logical record length for
137: .B list\ directed
138: and
139: .B namelist
140: I/O is relatively meaningless.
141: On output, the record length is dependent on the magnitude of the
142: data items.
143: On input, the record length is determined by the data types and the file
144: contents.
145: By ANSI definition, a slash, ``/'', terminates execution of a
146: list directed input operation.
147: Namelist input is terminated by ``&end'' or ``$end'' (depending on whether
148: the character before the namelist name was ``&'' or ``$'').
149: .Nh 3 "Internal I/O"
150: The logical record length for an
151: .B internal
152: read or write is the length of the
153: character variable or array element. Thus a simple character variable
154: is a single logical record. A character variable array is similar to
155: a fixed length direct access file, and obeys the same rules.
156: .B Unformatted
157: and
158: .B namelist
159: I/O are not allowed on ``internal'' files.
160: .Nh 2 "I/O execution"
161: Note that each execution of a
162: .Fo
163: .B unformatted
164: I/O statement causes a single
165: logical record to be read or written. Each execution of a
166: .Fo
167: .B formatted
168: I/O statement causes one or more logical records to be read or written.
169: .PP
170: A slash, ``/'', will terminate assignment of
171: values to the input list during
172: .B list\ directed
173: input and the remainder of the current input line is skipped.
174: The standard is rather vague on this point but seems to require that
175: a new external logical record be found at the start of any formatted
176: input. Therefore data following the slash is ignored and may be used
177: to comment the data file.
178: .PP
179: .B "Direct access list directed"
180: I/O is not allowed.
181: .B "Unformatted internal"
182: I/O is not allowed.
183: .B Namelist
184: I/O is allowed only with
185: .B "external sequential"
186: files.
187: All other flavors of I/O are allowed, although some are not part of the
188: .Sm ANSI
189: standard.
190: .PP
191: Any I/O statement may include an
192: .B err=
193: clause to specify an alternative branch to be taken on errors
194: and/or an
195: .B iostat=
196: clause to return the specific error code.
197: Any error detected during I/O processing will cause the program to abort
198: unless either
199: .B err=
200: or
201: .B iostat=
202: has been specificed in the program.
203: Read statements may include
204: .B end=
205: to branch on end-of-file.
206: The end-of-file indication for that logical unit may be reset with
207: a \fBbackspace\fP statement.
208: File position and the value of I/O list items is undefined following an error.
209: .sp 1
210: .Nh 1 "Implementation details"
211: Some details of the current implementation may be useful in understanding
212: constraints on
213: .Fo
214: I/O.
215: .Nh 2 "Number of logical units"
216: Unit numbers must be in the range 0 \- 99.
217: The maximum number of logical units that a program may have open at one
218: time is the same as the
219: .UX
220: system limit, currently 48.
221: .Nh 2 "Standard logical units"
222: By default, logical units 0, 5, and 6
223: are opened to ``stderr'', ``stdin'', and ``stdout'' respectively.
224: However they can be re-defined with an
225: .B open
226: statement.
227: To preserve error reporting, it is an error to close logical unit 0
228: although it may be reopened to another file.
229: .PP
230: If you want to open the default file name for any preconnected logical unit,
231: remember to
232: .B close
233: the unit first.
234: Redefining the standard units may impair normal console I/O.
235: An alternative is to
236: use shell re-direction to externally re-define the above units.
237: To re-define default blank control or format of the standard input or output
238: files, use the
239: .B open
240: statement specifying the unit number and no
241: file name (see \(sc\|2.4).
242: .PP
243: The standard units, 0, 5, and 6, are named internally ``stderr'', ``stdin'',
244: and ``stdout'' respectively.
245: These are not actual file names and can not be used for opening these units.
246: .B Inquire
247: will not return these names and will indicate
248: that the above units are not named unless they have been opened to real files.
249: The names are meant to make error reporting more meaningful.
250: .Nh 2 "Vertical format control"
251: Simple vertical format control is implemented. The logical unit must be opened
252: for sequential access with
253: .B "form = \(fmprint\(fm"
254: (see \(sc\|3.2).
255: Control codes ``0'' and ``1'' are replaced in the output file
256: with ``\\n'' and ``\\f'' respectively.
257: The control character ``+'' is not implemented and, like
258: any other character in the first position of a record
259: written to a ``print'' file, is dropped.
260: The
261: .B "form = \(fmprint\(fm"
262: mode does not recognize vertical format control for
263: .B "direct formatted, list directed,"
264: or
265: .B "namelist"
266: output.
267: .PP
268: An alternative is to use
269: the filter \fIfpr\fP(1) for vertical format control.
270: It replaces ``0'' and ``1'' by
271: ``\\n'' and ``\\f'' respectively, and implements the ``+'' control code.
272: Unlike
273: .B "form = \(fmprint\(fm"
274: which drops unrecognized form control characters, \fIfpr\fP copies those
275: characters to the output file.
276: .Nh 2 "File names and the open statement"
277: A file name may be specified in an \fBopen\fP statement for the
278: logical unit.
279: If a logical unit is opened by an \fBopen\fP statement which does
280: not specify a file name, or it is opened implicitly by the execution
281: of a \fBread\fP, \fBwrite\fP, or \fBendfile\fP
282: statement, then the default file name is
283: .I fort.N
284: where
285: .I N
286: is the logical unit number.
287: Before opening the file, the library checks for an environment
288: variable with a name identical to the tail of the
289: file name with periods removed.\(dg
290: .FS
291: \(dgPeriods are deleted because they can not be part of environment variable names in the Bourne shell.
292: .FE
293: If it finds such an environment variable, it uses its value
294: as the actual name of the file.
295: For example, a program containing:
296: .DS
297: open(32,file=\(fm/usr/guest/census/data.d\(fm)
298: read(32,100) vec
299: write(44) vec
300: .DE
301: normally will read from \fI/usr/guest/census/data.d\fP and write to
302: \fIfort.44\fP in the current directory.
303: If the environment variables \fIdatad\fP and \fIfort44\fP are set,
304: e.g.:
305: .DS
306: % setenv datad mydata
307: % setenv fort44 myout
308: .DE
309: in the C shell or:
310: .DS
311: $ datad=mydata
312: $ fort44=myout
313: $ export datad fort44
314: .DE
315: in the Bourne shell, then the program will read from \fImydata\fP and
316: write to \fImyout\fP.
317: .PP
318: An
319: .B open
320: statement need not specify a file name. If it refers to a logical
321: unit that is already open, the
322: .B blank=
323: and
324: .B form=
325: specifiers may be
326: redefined without affecting the current file position.
327: Otherwise, if
328: .B "status = \(fmscratch\(fm"
329: is specified, a temporary file with a
330: name of the form
331: .I tmp.FXXXXXX
332: will be opened,
333: and, by default, will be deleted when closed or during
334: termination of program execution.
335: .PP
336: It is an error to try to open an existing file with
337: .B "status = \(fmnew\(fm"
338: \&.
339: It is an error to try to open a nonexistent file with
340: .B "status = \(fmold\(fm"
341: \&.
342: By default,
343: .B "status = \(fmunknown\(fm"
344: will be assumed, and a file will be created if necessary.
345: .PP
346: By default, files are positioned
347: at their beginning upon opening, but see \fIfseek\fP(3f)
348: and \fIioinit\fP(3f) for alternatives.
349: Existing files are never truncated on opening.
350: Sequentially accessed external files are truncated to the current file
351: position on \fBclose\fP, \fBbackspace\fP, or \fBrewind\fP only if the last
352: access to the file was a write.
353: An
354: .B endfile
355: always causes such files to be truncated to the current
356: file position.
357: .Nh 2 "Format interpretation"
358: Formats which are in format statements are parsed by the compiler;
359: formats in \fBread\fP, \fBwrite\fP, and \fBprint\fP statements
360: are parsed during execution by the
361: .Sm I/O
362: library.
363: Upper as well as lower case characters are recognized in format statements
364: and all the alphabetic arguments to the I/O library routines.
365: .PP
366: If the external representation of a datum
367: is too large for the field width specified, the specified
368: field is filled with asterisks (\(**).
369: On \fBE\fPw.d\fBE\fPe output,
370: the exponent field will be filled with asterisks if the
371: exponent representation is too large.
372: This will only happen if ``e'' is zero (see appendix B).
373: .PP
374: On output, a real value that is truly zero will display as ``0.'' to
375: distinguish it from a very small non-zero value.
376: If this causes problems for other input systems, the
377: \fBBZ\fP edit descriptor may be used to cause the field
378: following the decimal point to be filled with zero's.
379: .PP
380: Non-destructive tabbing is implemented for both internal and external
381: formatted I/O.
382: Tabbing left or right on output
383: does not affect previously written portions of a record.
384: Tabbing right on output
385: causes unwritten portions of a record to be filled with blanks.
386: Tabbing right off the end of an input logical record is an error.
387: Tabbing left beyond the beginning of an input logical record leaves
388: the input pointer at the beginning of the record.
389: The format specifier
390: .B T
391: must be followed by a positive non-zero number.
392: If it is not, it will have a different meaning (see \(sc\|3.1).
393: .PP
394: Tabbing left requires seek ability on the logical unit.
395: Therefore it is not allowed in I/O to a terminal or pipe.
396: Likewise, nondestructive tabbing in either direction is possible
397: only on a unit that can seek. Otherwise tabbing right or spacing with
398: .B X
399: will write blanks on the output.
400: .Nh 2 "List directed output"
401: In formatting list directed output, the I/O system tries to prevent
402: output lines longer than 80 characters.
403: Each external datum will be separated by two spaces.
404: List directed output of
405: .B complex
406: values includes an appropriate comma.
407: List directed output distinguishes between
408: .B real
409: and
410: .B "double precision"
411: values and formats them differently.
412: Output of a character string that includes ``\\n''
413: is interpreted reasonably by the output system.
414: .Nh 2 "I/O errors"
415: If I/O errors are not trapped by the user's program an appropriate
416: error message will be written to ``stderr'' before aborting.
417: An error number will be printed in ``[ ]'' along with a brief error message
418: showing the logical unit and I/O state.
419: Error numbers < 100 refer to
420: .UX
421: errors, and are described in the
422: introduction to chapter 2 of the
423: .UX
424: Programmer's Manual.
425: Error numbers \(>= 100 come from the I/O library, and are described
426: further in the appendix to this writeup\(dd.
427: .FS
428: \(dd On many systems, these are also available in \fIhelp f77 io_err_msgs\fP.
429: .FE
430: For internal I/O, part of the string will be printed with ``|'' at the
431: current position in the string.
432: For external I/O, part of the current record will be displayed if
433: the error was caused during reading from a file that can backspace.
434: .sp 1
435: .Nh 1 "Non-``ANSI Standard'' extensions"
436: Several extensions have been added to the I/O system to provide
437: for functions omitted or poorly defined in the standard.
438: Programmers should be aware that these are non-portable.
439: .Nh 2 "Format specifiers"
440: .B B
441: is an acceptable edit control specifier. It causes return to the logical unit's
442: default mode of blank interpretation.
443: This is consistent with
444: .B S
445: which returns to default sign control.
446: .PP
447: .B P
448: by itself is equivalent to
449: .B 0P
450: \&. It resets the scale factor to the
451: default value, 0.
452: .PP
453: The form of the \fBE\fPw.d\fBE\fPe format specifier has been extended to
454: .B D
455: also.
456: The form \fBE\fPw.d.e is allowed but is not standard.
457: The ``e'' field specifies the minimum number of digits or spaces in the
458: exponent field on output.
459: If the value of the exponent is too large, the exponent notation
460: .B e
461: or
462: .B d
463: will be dropped from the output to allow one
464: more character position.
465: If this is still not adequate, the ``e'' field will be filled with
466: asterisks (\(**).
467: The default value for ``e'' is 2.
468: .PP
469: An additional form of tab control specification has been added.
470: The
471: .Sm ANSI
472: standard forms \fBTR\fPn, \fBTL\fPn, and \fBT\fPn are supported
473: where
474: .I n
475: is a positive non-zero number.
476: If
477: .B T
478: or n\fBT\fP is specified, tabbing will
479: be to the next (or n-th) 8-column tab stop.
480: Thus columns of alphanumerics can be lined up without counting.
481: .PP
482: A format control specifier has been added to suppress the newline
483: at the end of the last record of a formatted sequential write. The
484: specifier is a dollar sign ($). It is constrained by the same rules
485: as the colon (:). It is used typically for console prompts.
486: For example:
487:
488: .DS
489: write (\(**, "(\(fmenter value for x: \(fm,$)")
490: read (\(**,\(**) x
491: .DE
492: .PP
493: Radices other than 10 can be specified for formatted integer I/O
494: conversion. The specifier is patterned after
495: .B P,
496: the scale factor for
497: floating point conversion. It remains in effect until another radix is
498: specified or format interpretation is complete. The specifier is defined
499: as [n]\fBR\fP where 2 \(<= \fIn\fP \(<= 36. If
500: .I n
501: is omitted,
502: the default decimal radix is restored.
503: .PP
504: The format specifier \fBO\fPm.n may be used for an octal conversion;
505: it is equivalent to 8\fBR,I\fPm.n,10\fBR\fP.
506: Similarly, \fBZ\fPm.n is equivalent to 16\fBR,I\fPm.n,10\fBR\fP and
507: may be used for an hexadecimal conversion;
508: .PP
509: In conjunction with the above, a sign control specifier has been added
510: to cause integer values to be interpreted as unsigned during output
511: conversion. The specifier is
512: .B SU
513: and remains in effect until another
514: sign control specifier is encountered, or format interpretation is
515: complete.\(dg
516: .FS
517: \(dgNote: Unsigned integer values greater than (2\(**\(**31 - 1),
518: can be read and written using \fBSU\fP.
519: However they can not be used in
520: computations because
521: .Fo
522: uses signed arithmetic and such values appear to the arithmetic unit
523: as negative numbers.
524: .FE
525: Radix and ``unsigned'' specifiers could be used to format
526: a hexadecimal dump, as follows:
527:
528: .DS
529: 2000 format ( SU, 8Z10.8 )
530: .DE
531:
532: .Nh 2 "Print files"
533: The
534: .Sm ANSI
535: standard is ambiguous regarding the definition of a ``print'' file.
536: Since
537: .UX
538: has no default ``print'' file, an additional
539: .B form=
540: specifier
541: is now recognized in the
542: .B open
543: statement.
544: Specifying
545: .B "form = \(fmprint\(fm"
546: implies
547: .B formatted
548: and enables vertical format
549: control for that logical unit (see \(sc\|2.3).
550: Vertical format control is interpreted only on sequential formatted writes
551: to a ``print'' file.
552: .PP
553: The
554: .B inquire
555: statement will return
556: .B print
557: in the
558: .B form=
559: string variable
560: for logical units opened as ``print'' files.
561: It will return -1 for the unit number of an unconnected file.
562: .PP
563: If a logical unit is already open, an
564: .B open
565: statement including the
566: .B form=
567: option or the
568: .B blank=
569: option will do nothing but re-define those options.
570: This instance of the
571: .B open
572: statement need not include the file name, and
573: must not include a file name if
574: .B unit=
575: refers to a standard input or output.
576: Therefore, to re-define the standard output as a ``print'' file, use:
577:
578: .DS
579: open (unit=6, form=\(fmprint\(fm)
580: .DE
581: .Nh 2 "Scratch files"
582: A
583: .B close
584: statement with
585: .B "status = \(fmkeep\(fm"
586: may be specified for temporary files.
587: This is the default for all other files.
588: Remember to get the scratch file's real name,
589: using
590: .B inquire
591: \&, if you want to re-open it later.
592: .Nh 2 "List directed I/O"
593: List directed read has been modified to allow
594: tab characters wherever blanks are allowed.
595: It also allows input of a string not enclosed in quotes.
596: The string must not start with a digit or quote,
597: and can not contain any separators ( ``,'', ``/'', blank or tab ).
598: A newline will terminate the string unless escaped with \\.
599: Any string not meeting the above restrictions
600: must be enclosed in quotes (`` " '' or `` \(fm '').
601: .PP
602: Internal list directed I/O has been implemented. During internal list reads,
603: bytes are consumed until the iolist is satisfied, or the ``end-of-file''
604: is reached.
605: During internal list writes, records are filled until the iolist is satisfied.
606: The length of an internal array element should be at least 20 bytes to
607: avoid logical record overflow when writing double precision values.
608: Internal list read was implemented to make command line decoding easier.
609: Internal list write should be avoided.
610: .Nh 2 "Namelist I/O"
611: Namelist I/O is a common extension in Fortran systems.
612: The \fBf77\fP version was designed to be compatible with other
613: vendors versions;
614: it is described in ``A Portable Fortran 77 Compiler'',
615: by Feldman and Weinberger, August, 1985.
616: .sp 1
617: .Nh 1 "Running older programs"
618: Traditional
619: .Fo
620: environments usually assume carriage control on all logical units,
621: usually interpret blank spaces on input as ``0''s, and often provide
622: attachment of global file names to logical units at run time.
623: There are several routines in the I/O library to provide these functions.
624: .Nh 2 "Traditional unit control parameters"
625: If a program reads and writes only units 5 and 6, then including
626: .B \-lI66
627: in the f77 command will cause carriage control to be interpreted on
628: output and cause blanks to be zeros on input without further
629: modification of the program.
630: If this is not adequate,
631: the routine \fIioinit\fP(3f) can be called to specify control parameters
632: separately, including whether files should be positioned at their
633: beginning or end upon opening.
634: .Nh 2 "Ioinit()"
635: \fIIoinit\fP(3f) can be used to attach logical units
636: to specific files at run time, and to set global parameters for the
637: .Sm I/O
638: system.
639: It will look for names of a user specified form in the environment
640: and open the corresponding logical unit for
641: .B "sequential formatted"
642: I/O. Names must be of the form \fB\s-1PREFIX\s0\fP\fInn\fP where
643: .B \\s-1PREFIX\\s0
644: is specified in the call to
645: .I ioinit
646: and
647: .I nn
648: is the logical unit to be opened. Unit numbers < 10 must include
649: the leading ``0''.
650: .PP
651: .I Ioinit
652: should prove adequate for most programs as written.
653: However, it
654: is written in
655: .Fo \-77
656: specifically so that it may serve as an example for similar
657: user-supplied routines.
658: A copy may be retrieved by ``ar x /usr/lib/libU77.a ioinit.f''.
659: See \(sc\|2.4 for another way to override program file names
660: through environment variables.
661: .sp 1
662: .Nh 1 "Magnetic tape I/O"
663: Because the I/O library uses stdio buffering, reading or writing
664: magnetic tapes should be done with great caution, or avoided if possible.
665: A set of routines has been provided to read and write arbitrary sized buffers
666: to or from tape directly. The buffer must be a
667: .B character
668: object.
669: .B Internal
670: I/O can be used to fill or interpret the buffer.
671: These routines do not use normal
672: .Fo
673: I/O processing and do not obey
674: .Fo
675: I/O rules.
676: See \fItopen\fP(3f).
677: .sp 1
678: .Nh 1 "Caveat Programmer"
679: The I/O library is extremely complex yet we believe there are few bugs left.
680: We've tried to make the system as correct as possible according to
681: the
682: .Sm ANSI
683: X3.9\-1978 document and keep it compatible with the
684: .UX
685: file system.
686: Exceptions to the standard are noted in appendix B.
687: .bp
688: .DS C
689: .B "Appendix A"
690:
691: .B "I/O Library Error Messages"
692: .DE
693: .XS
694: Appendix A: I/O Library Error Messages
695: .XE
696: .sp 1
697: .PP
698: The following error messages are generated by the I/O library.
699: The error numbers are returned in the \fBiostat=\fP variable.
700: Error numbers < 100 are generated by the
701: .UX
702: kernel.
703: See the introduction to chapter 2 of the
704: .UX
705: Programmers Manual for their description.
706: .nr PD 0
707: .de Er
708: .ne 4v
709: .IP \\$1
710: \fI\\$2\fP
711: .br
712: ..
713: .RS
714:
715: .Er 100 "error in format"
716: See error message output for the location
717: of the error in the format. Can be caused
718: by more than 10 levels of nested parentheses, or
719: an extremely long format statement.
720:
721: .Er 101 "illegal unit number"
722: It is illegal to close logical unit 0.
723: Unit numbers must be between 0 and 99 inclusive.
724:
725: .Er 102 "formatted i/o not allowed"
726: The logical unit was opened for
727: unformatted I/O.
728:
729: .Er 103 "unformatted i/o not allowed"
730: The logical unit was opened for
731: formatted I/O.
732:
733: .Er 104 "direct i/o not allowed"
734: The logical unit was opened for sequential
735: access, or the logical record length was
736: specified as 0.
737:
738: .Er 105 "sequential i/o not allowed"
739: The logical unit was opened for direct
740: access I/O.
741:
742: .Er 106 "can't backspace file"
743: The file associated with the logical unit
744: can't seek. May be a device or a pipe.
745:
746: .Er 107 "off beginning of record"
747: The format specified a left tab beyond the
748: beginning of an internal input record.
749:
750: .Er 108 "can't stat file"
751: The system can't return status information
752: about the file. Perhaps the directory is
753: unreadable.
754:
755: .Er 109 "no \(** after repeat count"
756: Repeat counts in list directed I/O must be
757: followed by an \(** with no blank spaces.
758:
759: .Er 110 "off end of record"
760: A formatted write tried to go beyond the
761: logical end-of-record. An unformatted read
762: or write will also cause this.
763:
764: .Er 111 "truncation failed"
765: The truncation of an external sequential file on
766: .B close ,
767: .B backspace ,
768: .B rewind ,
769: or
770: .B endfile
771: failed.
772:
773: .Er 112 "incomprehensible list input"
774: List input has to be just right.
775:
776: .Er 113 "out of free space"
777: The library dynamically creates buffers for
778: internal use. You ran out of memory for this.
779: Your program is too big!
780:
781: .Er 114 "unit not connected"
782: The logical unit was not open.
783:
784: .Er 115 "invalid data for integer format term"
785: Only spaces, a leading sign and digits are allowed.
786:
787: .Er 116 "invalid data for logical format term"
788: Legal input consists of spaces (optional), a period (optional), and then
789: a ``t'', ``T'', ``f'', or ``F''.
790:
791: .Er 117 "\|\(fmnew\|\(fm file exists"
792: You tried to open an existing file with
793: ``status=\|\(fmnew\|\(fm''.
794:
795: .Er 118 "can't find \|\(fmold\|\(fm file"
796: You tried to open a non-existent file
797: with ``status=\|\(fmold\|\(fm''.
798:
799: .Er 119 "opening too many files or unknown system error"
800: Either you are trying to open too many files
801: simultaneously or there has been an undetected system error.
802:
803: .Er 120 "requires seek ability"
804: Direct access requires seek ability.
805: Sequential unformatted I/O requires seek
806: ability on the file due to the special
807: data structure required. Tabbing left
808: also requires seek ability.
809:
810: .Er 121 "illegal argument"
811: Certain arguments to
812: .B open ,
813: etc. will be
814: checked for legitimacy. Often only non-default
815: forms are looked for.
816:
817: .Er 122 "negative repeat count"
818: The repeat count for list directed input
819: must be a positive integer.
820:
821: .Er 123 "illegal operation for unit"
822: An operation was requested for a device
823: associated with the logical unit which
824: was not possible. This error is returned
825: by the tape I/O routines if attempting to
826: read past end-of-tape, etc.
827:
828: .Er 124 "invalid data for d, e, f or g format term"
829: Input data must be legal.
830:
831: .Er 125 "illegal input for namelist"
832: Column one of input is ignored, the namelist name
833: must match, the variables must be in the namelist,
834: and the data must be of the right type.
835: .if n .nr PD 1v
836: .if t .nr PD 0.3v
837: .RE
838: .bp
839: .LP
840: .DS C
841: .B "Appendix B"
842:
843: .B "Exceptions to the ANSI Standard"
844: .DE
845: .XS
846: Appendix B: Exceptions to the ANSI Standard
847: .XE
848: .sp 1
849: .PP
850: A few exceptions to the
851: .Sm ANSI
852: standard remain.
853: .sp 1
854: .LP
855: .B "Vertical format control"
856: .PP
857: The ``+'' carriage control specifier is not fully implemented
858: (see \(sc\|2.3).
859: It would be difficult to implement it correctly and still
860: provide
861: .UX -like
862: file I/O.
863: .PP
864: Furthermore, the carriage control implementation is asymmetrical.
865: A file written with carriage control interpretation can not be
866: read again with the same characters in column 1.
867: .PP
868: An alternative to interpreting carriage control internally is to
869: run the output file through a ``Fortran output filter''
870: before printing. This filter could recognize a much broader range
871: of carriage control and include terminal dependent processing.
872: One such filter is \fIfpr\fP(1).
873: .sp 1
874: .LP
875: .B "Default files"
876: .PP
877: Files created by default use of
878: .B endfile
879: statements are opened for
880: .B "sequential formatted"
881: access. There is no way to redefine such a file to allow
882: .B direct
883: or
884: .B unformatted
885: access.
886: .sp 1
887: .LP
888: .B "Lower case strings"
889: .PP
890: It is not clear if the
891: .Sm ANSI
892: standard requires internally generated strings to be upper case or not.
893: As currently written, the
894: .B inquire
895: statement will return lower case strings for any alphanumeric data.
896: .sp 1
897: .LP
898: .B "Exponent representation on Ew.dEe output"
899: .PP
900: If the field width for the exponent is too small, the standard
901: allows dropping the exponent character but only if the exponent
902: is > 99. This system does not enforce that restriction.
903: Further, the standard implies that the entire field, ``w'', should be
904: filled with asterisks if the exponent can not be displayed.
905: This system fills only the exponent field in the above case since
906: that is more diagnostic.
907: .sp 1
908: .LP
909: .B "Pre-connection of files"
910: .PP
911: The standard says units must be pre-connected to files before the program
912: starts or must be explicitly opened.
913: Instead, the I/O library
914: connects the unit to a file on its first use in a
915: \fBread\fP, \fBwrite\fP, \fBprint\fP, or \fBendfile\fP statement.
916: Thus \fBinquire\fP by unit can not tell prior to a unit number use the
917: characteristics or name of the file corresponding to a unit.
918: .\" want Table of Contents to begin on page 2 hence must expand body
919: .\" of .TC macro to enable us to get handle on page number.
920: .pn 2
921: .bp
922: .PX
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