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1.1 ! root 1: ! 2: ! 3: ! 4: ! 5: ! 6: ! 7: ! 8: ! 9: ! 10: Update to the f77 I/O Library ! 11: January 1980 ! 12: ! 13: ! 14: David L. Wasley ! 15: ! 16: University of California ! 17: Berkeley, Calif. 94720 ! 18: ! 19: ! 20: ! 21: ! 22: ! 23: The fortran-77 I/O library, libI77.a, has been exten- ! 24: sively updated. All known bugs have been fixed, and I/O ! 25: error reporting has been improved. Several non-standard ! 26: extensions to FORTRAN I/O have been added. ! 27: ! 28: Some general concepts regarding f77 I/O deserve clarif- ! 29: ication. There are three forms of I/O: formatted, unformat- ! 30: ted, and list-directed. The last is related to formatted but ! 31: does not obey all the rules for formatted I/O. There are ! 32: two modes of access to external and internal files: direct ! 33: and sequential. The definition of a logical record depends ! 34: upon the combination of I/O form and mode specified by the ! 35: fortran I/O statement. ! 36: ! 37: A logical record in direct access external files is a ! 38: string of bytes of a length specified when the file is ! 39: opened. Read and write statements must not specify logical ! 40: records longer than the original record size definition. ! 41: Shorter logical records are allowed. Unformatted direct ! 42: writes leave the unfilled part of the record undefined. ! 43: Formatted direct writes cause the unfilled record to be pad- ! 44: ded with blanks. ! 45: ! 46: Logical records in sequentially accessed external files ! 47: may be of arbitrary and variable length. Logical record ! 48: length for unformatted sequential files is determined by the ! 49: size of items in the iolist. For formatted write state- ! 50: ments, logical record length is determined by the format ! 51: statement interacting with the iolist at execution time. ! 52: Formatted sequential access causes one or more logical ! 53: records ending with 'newline' characters to be read or writ- ! 54: ten. ! 55: ! 56: Logical record length for list-directed I/O is rela- ! 57: tively meaningless. On output, the record length is depen- ! 58: dent on the magnitude of the data items. On input, the ! 59: record length is determined by the data types and the file ! 60: contents. ! 61: ! 62: ! 63: ! 64: ! 65: ! 66: ! 67: ! 68: ! 69: ! 70: - 2 - ! 71: ! 72: ! 73: The logical record length for "internal" files is the ! 74: length of the character variable or array element. Thus a ! 75: simple character variable is a single logical record. A ! 76: character variable array is similar to a fixed length direct ! 77: access file, and obeys the same rules. Unformatted I/O is ! 78: not allowed on "internal" files. ! 79: ! 80: Note that each execution of a fortran unformatted I/O ! 81: statement causes a single logical record to be read or writ- ! 82: ten. Each execution of a fortran formatted I/O statement ! 83: causes one or more logical records to be read or written. ! 84: ! 85: Any error detected during I/O processing will cause the ! 86: program to abort unless alternate action has been provided ! 87: for specifically in the program. Any I/O statement may ! 88: include an err= clause (and iostat= clause) to specify an ! 89: alternate branch to be taken on errors (and return the ! 90: specific error code). Read or write statements may include ! 91: end= to branch on end-of-file. File position and the value ! 92: of I/O list items is undefined following an error. ! 93: ! 94: I. Implementation details. ! 95: ! 96: The maximum number of logical units that a program may ! 97: have open at one time has been set to correspond with the ! 98: UNIX system limit, currently 20. However, the I/O library ! 99: uses UNIX file access for internal purposes. Therefore ! 100: fatal errors are possible if the maximum number of files are ! 101: open. Specifically, 'close' or 'endfile' on an old file, ! 102: and "'inquire' by file" may fail. ! 103: ! 104: Vertical format control is implemented. The logical ! 105: unit must be opened for sequential access and "form = ! 106: 'print'" (see below). Control codes '0' and '1' are ! 107: replaced in the output file with '\n' and '\f' respectively. ! 108: The control character '+' isn't implemented and, like any ! 109: other character in the first position of a record written to ! 110: a "print" file, is dropped. No vertical format control is ! 111: recognized for direct formatted output or list directed out- ! 112: put. ! 113: ! 114: Default logical units 0, 5, and 6 can be re-defined ! 115: with an 'open' statement. To preserve error reporting, it ! 116: is an error to close logical unit 0. If you want to open ! 117: the default filename for any preconnected logical unit, ! 118: remember to 'close' the unit first. Redefining the standard ! 119: units may impair normal console I/O. An alternative is to ! 120: use shell re-direction to externally re-define the above ! 121: units. To re-define default blank control or format of the ! 122: standard input or output files, use the 'open' statement ! 123: specifying the unit number and no filename (see below). ! 124: ! 125: An 'open' statement need not specify a filename. If it ! 126: refers to a logical unit that is already open, the "blank= " ! 127: ! 128: ! 129: ! 130: ! 131: ! 132: ! 133: ! 134: ! 135: ! 136: - 3 - ! 137: ! 138: ! 139: and "form= " specifiers may be redefined without affecting ! 140: the current file position. Otherwise, if "status='scratch'" ! 141: is specified, a temporary file with a name of the form ! 142: 'tmp.FXXXXXX' will be opened, and, by default, will be ! 143: deleted when closed or during termination of program execu- ! 144: tion. Any other "status= " specifier without an associated ! 145: filename results in opening a file named 'fort.N' where N is ! 146: the specified logical unit number. It is an error to try to ! 147: open an existing file with "status='new'". It is an error ! 148: to try to open a nonexistent file with "status='old'". By ! 149: default "status='unknown'" will be assumed, and a file will ! 150: be created if necessary. Existing files are never truncated ! 151: on opening but are positioned at the end-of-file. ! 152: ! 153: Sequentially accessed external files are truncated to ! 154: the current file position on 'close', 'backspace', or ! 155: 'rewind' only if the last access to the file was a write. ! 156: ! 157: Upper as well as lower case characters are recognized ! 158: in format statements and all alphabetic arguments to the I/O ! 159: library routines. This has always been true for statements ! 160: that are part of the source code, but not for format state- ! 161: ments or character arguments from a file. ! 162: ! 163: If the external representation of a datum is too large ! 164: for the field width specified, the specified field is filled ! 165: with asterisks (*). On 'Ew.dEe' output, the e field will be ! 166: filled with asterisks if the exponent representation is too ! 167: large. (This will only happen if e==0) ! 168: ! 169: List-directed output of complex values now includes an ! 170: appropriate comma. List-directed output now distinguishes ! 171: between real*4 and real*8 values and formats them dif- ! 172: ferently. Output of a character string that includes '\n' ! 173: now works correctly. ! 174: ! 175: If I/O errors are not trapped by the user's program an ! 176: appropriate error message will be written to 'stderr' before ! 177: aborting. An error number will be printed in [ ] along with ! 178: a brief error message showing the logical unit and I/O ! 179: state. Error numbers < 100 refer to UNIX errors, and are ! 180: described in the introduction to chapter 2 of the UNIX ! 181: Programmer's Manual. Error numbers >= 100 come from the I/O ! 182: library, and are described further in the appendix to this ! 183: writeup. For internal I/O, part of the string will be ! 184: printed with '|' at the current position in the string. For ! 185: external I/O, part of the current record will be displayed ! 186: if the error was caused during reading from a file that can ! 187: backspace. ! 188: ! 189: Direct access list-directed I/O is not allowed. Unfor- ! 190: matted internal I/O is not allowed. Both the above will be ! 191: caught by the compiler. All other flavors of I/O are ! 192: allowed, although some are not part of the ANSI standard. ! 193: ! 194: ! 195: ! 196: ! 197: ! 198: ! 199: ! 200: ! 201: ! 202: - 4 - ! 203: ! 204: ! 205: The standard units, 0, 5, and 6, are now named inter- ! 206: nally 'stderr', 'stdin', and 'stdout' respectively. These ! 207: are not actual filenames and can not be used for opening ! 208: these units. 'inquire' will not return these names and will ! 209: indicate that the above units are not named unless they have ! 210: been opened to real files. The names are meant to make ! 211: error reporting more meaningful. ! 212: ! 213: On output, a real value that is truly zero will display ! 214: as '0.' to distinguish it from a very small non-zero value. ! 215: This occurs in 'F', 'E', 'D', and 'G' format conversions. ! 216: ! 217: Non-destructive tabbing is implemented for both inter- ! 218: nal and external formatted I/O. Tabbing left or right on ! 219: output does not affect previously written portions of a ! 220: record. Tabbing right on output causes unwritten portions ! 221: of a record to be filled with blanks. Tabbing left or right ! 222: off the end of a logical record is an error. The format ! 223: specifier 'T' must be followed by a positive non-zero ! 224: number. If it is not, it will have a different meaning (See ! 225: below). Note that spacing with 'X' always writes blanks in ! 226: the output record. ! 227: ! 228: II. Non-"ANSI Standard" Extensions ! 229: ! 230: B is an acceptable edit control specifier. It causes ! 231: return to the default mode of blank interpretation (NULL) ! 232: and is identical to BN. This is consistent with S which ! 233: returns to default sign control. ! 234: ! 235: P by itself is equivalent to 0P. It resets the scale ! 236: factor to the default value, 0. ! 237: ! 238: The form of the 'Ew.dEe' format specifier has been ! 239: extended to 'D' also. The form 'Ew.d.e' is allowed but is ! 240: not standard. The 'e' field specifies the minimum number of ! 241: digits or spaces in the exponent field on output. If the ! 242: value of the exponent is too large, the exponent notation ! 243: 'e' or 'd' will be dropped from the output to allow one more ! 244: character position. If this is still not adequate, the 'e' ! 245: field will be filled with asterisks (*). The default value ! 246: for 'e' is 2. ! 247: ! 248: An additional form of tab control specification has ! 249: been added. The ANSI standard forms 'TRn', 'TLn', and 'Tn' ! 250: are supported where n is a positive non-zero number. If 'T' ! 251: or 'nT' is specified, tabbing will be to the next (or n-th) ! 252: 8-column tab stop. Thus columns of alphanumerics can be ! 253: lined up without counting. (See above for a description of ! 254: the tabbing implementation.) ! 255: ! 256: A format control specifier has been added to suppress ! 257: the newline at the end of the last record of a formatted ! 258: sequential write. The specifier is a dollar sign ($). It is ! 259: ! 260: ! 261: ! 262: ! 263: ! 264: ! 265: ! 266: ! 267: ! 268: - 5 - ! 269: ! 270: ! 271: constrained by the same rules as the colon (:). It is used ! 272: typically for console prompts. For example: ! 273: ! 274: ! 275: write (*, "('enter value for x: ',$)") ! 276: read (*,*) x ! 277: ! 278: ! 279: Radices other than 10 can be specified for formatted ! 280: integer I/O conversion. The specifier is patterned after P, ! 281: the pre-scale factor for floating point conversion. It ! 282: remains in effect until another radix is specified or format ! 283: interpretation is complete. The specifier is defined as [n]R ! 284: where 2 <= n <= 36. If n is omitted, the default decimal ! 285: radix is restored. ! 286: ! 287: In conjunction with the above, a sign control specifier ! 288: has been added to cause integer values to be interpreted as ! 289: unsigned during output conversion. The specifier is SU and ! 290: remains in effect until another sign control specifier is ! 291: encountered, or format interpretation is complete. Radix and ! 292: 'unsigned' specifiers could be used to format a hexadecimal ! 293: dump, as follows: ! 294: ! 295: ! 296: 2000 format( SU, 16R, 8I10.8) ! 297: ! 298: ! 299: Note: Unsigned integer values greater than (2**30 - 1), i.e. ! 300: any signed negative value, can not be read by FORTRAN input ! 301: routines. All internal values will be output correctly. ! 302: ! 303: The ANSI standard is ambiguous regarding the definition ! 304: of a "print" file. Since UNIX has no default "print" file, ! 305: an additional 'form' specifier is now recognized in the ! 306: 'open' statement. Specifying "form='print'" implies 'for- ! 307: matted' and enables vertical format control for that logical ! 308: unit (see above). Vertical format control is interpreted ! 309: only on sequential formatted writes to a "print" file. ! 310: ! 311: The 'inquire' statement will return 'print' in the ! 312: 'FORM=' string variable for logical units opened as "print" ! 313: files. It will return -1 for the unit number of an uncon- ! 314: nected file. ! 315: ! 316: If a logical unit is already open, an 'open' statement ! 317: including the re-define those options. This instance of the ! 318: 'open' statement need not include the filename, and must not ! 319: include a filename if 'unit=' refers to the standard input ! 320: or outputs. Therefore, to re-define the standard output as ! 321: a "print" file, use: ! 322: ! 323: ! 324: open (unit=6, form='print') ! 325: ! 326: ! 327: ! 328: ! 329: ! 330: ! 331: ! 332: ! 333: ! 334: - 6 - ! 335: ! 336: ! 337: In a 'close' statement, "status='keep'" may be speci- ! 338: fied for temporary files. This is the default for all other ! 339: files. Remember to get the file's real name, using ! 340: 'inquire', if you want to re-open it later. ! 341: ! 342: List directed read has been modified to allow input of ! 343: a string not enclosed in quotes. The string must not start ! 344: with a digit, and can not contain a separator (, or /) or ! 345: blank (space or tab). A newline will terminate the string ! 346: unless escaped with \. Any string not meeting the above res- ! 347: trictions must be enclosed in quotes (" or '). ! 348: ! 349: Internal list-directed I/O has been implemented. During ! 350: internal list reads, bytes are consummed until the iolist is ! 351: satisfied, or the 'end-of-file' is reached. During internal ! 352: list writes, records are filled until the iolist is satis- ! 353: fied. The length of an internal array element should be at ! 354: least 20 bytes to avoid logical record overflow when writing ! 355: double precision values. Internal list read was implemented ! 356: to make command line decoding easier. Internal list write ! 357: should be avoided. ! 358: ! 359: ! 360: ! 361: ! 362: ! 363: ! 364: ! 365: ! 366: ! 367: ! 368: ! 369: ! 370: ! 371: ! 372: ! 373: ! 374: ! 375: ! 376: ! 377: ! 378: ! 379: ! 380: ! 381: ! 382: ! 383: ! 384: ! 385: ! 386: ! 387: ! 388: ! 389: ! 390: ! 391: ! 392: ! 393: ! 394: ! 395: ! 396: ! 397: ! 398: ! 399: ! 400: - 7 - ! 401: ! 402: ! 403: Appendix A ! 404: I/O Library Error Messages ! 405: ! 406: The following error messages are generated by the I/O ! 407: library. The error numbers are returned in the "iostat=" ! 408: variable if the "err=" return is taken. Error numbers < 100 ! 409: are generated by UNIX. See the UNIX Programmers Manual, ! 410: introduction to chapter 2. ! 411: ! 412: /* 100 */ "error in format" ! 413: See error message output for the location ! 414: of the error in the format. Can be caused ! 415: by more than 10 levels of nested (), or ! 416: an extremely long format statement. ! 417: ! 418: /* 101 */ "illegal unit number" ! 419: It is illegal to close logical unit 0. ! 420: Negative unit numbers are not allowed. ! 421: The upper limit is system dependent. ! 422: ! 423: /* 102 */ "formatted io not allowed" ! 424: The logical unit was opened for ! 425: unformatted I/O. ! 426: ! 427: /* 103 */ "unformatted io not allowed" ! 428: The logical unit was opened for ! 429: formatted I/O. ! 430: ! 431: /* 104 */ "direct io not allowed" ! 432: The logical unit was opened for sequential ! 433: access, or the logical record length was ! 434: specified as 0. ! 435: ! 436: /* 105 */ "sequential io not allowed" ! 437: The logical unit was opened for direct ! 438: access I/O. ! 439: ! 440: /* 106 */ "can't backspace file" ! 441: The file associated with the logical unit ! 442: can't seek. May be a device or a pipe. ! 443: ! 444: /* 107 */ "off beginning of record" ! 445: The format specified a left tab off the ! 446: beginning of the record. ! 447: ! 448: /* 108 */ "can't stat file" ! 449: The system can't return status information ! 450: about the file. Perhaps the directory is ! 451: unreadable. ! 452: ! 453: /* 109 */ "no * after repeat count" ! 454: Repeat counts in list-directed I/O must be ! 455: followed by an * with no blank spaces. ! 456: ! 457: ! 458: ! 459: ! 460: ! 461: ! 462: ! 463: ! 464: ! 465: ! 466: - 8 - ! 467: ! 468: ! 469: /* 110 */ "off end of record" ! 470: A formatted write tried to go beyond the ! 471: logical end-of-record. An unformatted read ! 472: or write will also cause this. ! 473: ! 474: /* 111 */ "truncation failed" ! 475: The truncation of external sequential files ! 476: on 'close', 'backspace', or 'rewind' tries ! 477: to do a copy. It failed. Perhaps the temp ! 478: file couldn't be created. ! 479: ! 480: /* 112 */ "incomprehensible list input" ! 481: List input has to be just right. ! 482: ! 483: /* 113 */ "out of free space" ! 484: The library dynamically creates buffers for ! 485: internal use. You ran out of memory for this. ! 486: Your program is too big! ! 487: ! 488: /* 114 */ "unit not connected" ! 489: The logical unit was not open. ! 490: ! 491: /* 115 */ "read unexpected character" ! 492: Certain format conversions can't tolerate ! 493: non-numeric data. Logical data must be ! 494: T or F. ! 495: ! 496: /* 116 */ "blank logical input field" ! 497: ! 498: /* 117 */ "'new' file exists" ! 499: You tried to open an existing file with ! 500: "status='new'". ! 501: ! 502: /* 118 */ "can't find 'old' file" ! 503: You tried to open a non-existent file ! 504: with "status='old'". ! 505: ! 506: /* 119 */ "unknown system error" ! 507: Shouldn't happen, but ..... ! 508: (Send me a documented example.) ! 509: ! 510: /* 120 */ "requires seek ability" ! 511: Direct access requires seek ability. ! 512: Sequential unformatted I/O requires seek ! 513: ability on the file due to the special ! 514: data structure required. Tabbing left ! 515: also requires seek ability. ! 516: ! 517: /* 121 */ "illegal argument" ! 518: Certain arguments to 'open', etc. will be ! 519: checked for legitimacy. Often only non- ! 520: default forms are looked for. ! 521: ! 522: ! 523: ! 524: ! 525: ! 526: ! 527: ! 528:
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