![[BACK]](/cvsweb/icons/back.gif){kind=icon}
Return to writeup.tx CVS log ![[TXT]](/cvsweb/icons/text.gif){kind=icon}
![[DIR]](/cvsweb/icons/dir.gif){kind=icon}
Up to [CSRG BSD Unix] / 41BSD / lib / libI77uc|
Return to writeup.tx CVS log | Up to [CSRG BSD Unix] / 41BSD / lib / libI77uc |
1.1 ! root 1: .ND ! 2: .nr ll 7.0i ! 3: .nr LL 7.0i ! 4: .TL ! 5: Update to the f77 I/O Library ! 6: September 1980 ! 7: .AU ! 8: David L. Wasley ! 9: .AI ! 10: University of California ! 11: Berkeley, Calif. 94720 ! 12: .PP ! 13: The fortran-77 I/O library, libI77.a, ! 14: performs all the various types of formatted and unformatted FORTRAN ! 15: input and output. ! 16: I/O error reporting is generated by these routines. ! 17: Several non-standard extensions to FORTRAN I/O have been added. ! 18: These routines use the C stdio library for it's efficient buffering scheme. ! 19: .PP ! 20: Some general concepts regarding f77 I/O deserve clarification. There are three ! 21: forms of I/O: formatted, unformatted, and list-directed. The last is ! 22: related to formatted but does not obey all the rules for formatted I/O. ! 23: There are two modes of access to external and internal files: direct ! 24: and sequential. The definition of a logical record depends upon the ! 25: combination of I/O form and mode specified by the fortran I/O statement. ! 26: .PP ! 27: A logical record in direct access external files is a string of bytes ! 28: of a length specified when the file is opened. ! 29: Read and write statements must not specify logical records longer than ! 30: the original record size definition. Shorter logical records are allowed. ! 31: Unformatted direct writes leave the unfilled part of the record undefined. ! 32: Formatted direct writes cause the unfilled record to be padded with blanks. ! 33: .PP ! 34: Logical records in sequentially accessed external files may be of arbitrary ! 35: and variable length. ! 36: Logical record length for unformatted sequential files is determined by ! 37: the size of items in the iolist. ! 38: For formatted write statements, logical record length is determined by ! 39: the format statement interacting with the iolist at execution time. ! 40: Formatted sequential access causes one or more logical records ! 41: ending with newline characters to be read or written. ! 42: .PP ! 43: Logical record length for list-directed I/O is relatively meaningless. ! 44: On output, the record length is dependent on the magnitude of the ! 45: data items. ! 46: On input, the record length is determined by the data types and the file ! 47: contents. ! 48: An input record will be terminated by the occurance of a slash, ``/'', ! 49: that is not part of a character string datum, ! 50: and any input list items that have not been read will remain unchanged. ! 51: If the input list is exhausted, the input stream is flushed ! 52: until the next occurance of either a slash, or a newline (or end-of-file). ! 53: .PP ! 54: The logical record length for "internal" files is the length of the ! 55: character variable or array element. Thus a simple character variable ! 56: is a single logical record. A character variable array is similar to ! 57: a fixed length direct access file, and obeys the same rules. ! 58: Unformatted I/O is not allowed on "internal" files. ! 59: .PP ! 60: Note that each execution of a fortran unformatted I/O statement causes a single ! 61: logical record to be read or written. Each execution of a fortran formatted ! 62: I/O statement causes one or more logical records to be read or written. ! 63: .PP ! 64: Any error detected during I/O processing will cause the program to abort ! 65: unless alternate action has been provided for specifically in the program. ! 66: Any I/O statement may include an err= clause (and iostat= clause) ! 67: to specify an ! 68: alternate branch to be taken on errors (and return the specific error code). ! 69: Read or write statements may include end= to branch on end-of-file. ! 70: File position and the value of I/O list items is undefined following an error. ! 71: ! 72: I. Implementation details. ! 73: .PP ! 74: The maximum number of logical units that a program may have open at one ! 75: time has been set to correspond with the UNIX system limit, currently 20. ! 76: However, the I/O library uses UNIX file access for internal purposes. ! 77: Therefore fatal errors are possible if the maximum number of files are open. ! 78: Specifically, 'close' or 'endfile' on an old file, ! 79: and "'inquire' by file" may fail. ! 80: .PP ! 81: Vertical format control is implemented. The logical unit must be opened ! 82: for sequential access and "form = 'print'" (see below). ! 83: Control codes '0' and '1' are replaced in the output file ! 84: with '\\n' and '\\f' respectively. ! 85: The control character '+' isn't implemented and, like ! 86: any other character in the first position of a record ! 87: written to a "print" file, is dropped. ! 88: No vertical format control is recognized for direct formatted output ! 89: or list directed output. ! 90: .PP ! 91: Default logical units 0, 5, and 6 can be re-defined with an 'open' statement. ! 92: To preserve error reporting, it is an error to close logical unit 0. ! 93: If you want to open the default filename for any preconnected logical unit, ! 94: remember to 'close' the unit first. ! 95: Redefining the standard units may impair normal console I/O. ! 96: An alternative is to ! 97: use shell re-direction to externally re-define the above units. ! 98: To re-define default blank control or format of the standard input or output ! 99: files, use the 'open' statement specifying the unit number and no ! 100: filename (see below). ! 101: .PP ! 102: An 'open' statement need not specify a filename. If it refers to a logical ! 103: unit that is already open, the "blank= " and "form= " specifiers may be ! 104: redefined without affecting the current file position. ! 105: Otherwise, if "status='scratch'" is specified, a temporary file with a ! 106: name of the form 'tmp.FXXXXXX' will be opened, ! 107: and, by default, will be deleted when closed or during ! 108: termination of program execution. ! 109: Any other "status= " specifier without an associated filename results in ! 110: opening a file named 'fort.N' where N is the specified logical unit number. ! 111: It is an error to try to open an existing file with "status='new'". ! 112: It is an error to try to open a nonexistent file with "status='old'". ! 113: By default "status='unknown'" will be assumed, and a file will be created ! 114: if necessary. ! 115: Existing files are never truncated on opening but are positioned ! 116: at the end-of-file. ! 117: .PP ! 118: Sequentially accessed external files are truncated to the current file ! 119: position on 'close', 'backspace', or 'rewind' only if the last ! 120: access to the file was a write. ! 121: .PP ! 122: Upper as well as lower case characters are recognized in format statements ! 123: and all alphabetic arguments to the I/O library routines. ! 124: This has always been true for statements that are ! 125: part of the source code, but not for format statements ! 126: or character arguments from a file. ! 127: .PP ! 128: If the external representation of a datum ! 129: is too large for the field width specified, the specified ! 130: field is filled with asterisks (*). ! 131: On 'Ew.dEe' output, the e field will be filled with asterisks if the ! 132: exponent representation is too large. ! 133: (This will only happen if e==0) ! 134: .PP ! 135: List-directed output of complex values now includes an appropriate comma. ! 136: List-directed output now distinguishes between real*4 and real*8 values ! 137: and formats them differently. ! 138: Output of a character string that includes '\\n' now works correctly. ! 139: .PP ! 140: If I/O errors are not trapped by the user's program an appropriate ! 141: error message will be written to 'stderr' before aborting. ! 142: An error number will be printed in [ ] along with a brief error message ! 143: showing the logical unit and I/O state. ! 144: Error numbers < 100 refer to UNIX errors, and are described in the ! 145: introduction to chapter 2 of the UNIX Programmer's Manual. ! 146: Error numbers >= 100 come from the I/O library, and are described ! 147: further in the appendix to this writeup. ! 148: For internal I/O, part of the string will be printed with '|' at the ! 149: current position in the string. ! 150: For external I/O, part of the current record will be displayed if ! 151: the error was caused during reading from a file that can backspace. ! 152: .PP ! 153: Direct access list-directed I/O is not allowed. ! 154: Unformatted internal I/O is not allowed. ! 155: Both the above will be caught by the compiler. ! 156: All other flavors of I/O are allowed, although some are not part of the ANSI ! 157: standard. ! 158: .PP ! 159: The standard units, 0, 5, and 6, are now named internally 'stderr', 'stdin', ! 160: and 'stdout' respectively. ! 161: These are not actual filenames and can not be used for opening these units. ! 162: \'inquire' will not return these names and will indicate ! 163: that the above units are not named unless they have been opened to real files. ! 164: The names are meant to make error reporting more meaningful. ! 165: .PP ! 166: On output, a real value that is truly zero will display as '0.' to ! 167: distinguish it from a very small non-zero value. ! 168: This occurs in 'F', 'E', 'D', and 'G' format conversions. ! 169: .PP ! 170: Non-destructive tabbing is implemented for both internal and external ! 171: formatted I/O. ! 172: Tabbing left or right on output ! 173: does not affect previously written portions of a record. ! 174: Tabbing right on output ! 175: causes unwritten portions of a record to be filled with blanks. ! 176: Tabbing left or right off the end of a logical record is an error. ! 177: The format specifier 'T' must be followed by a positive non-zero number. ! 178: If it is not, it will have a different meaning (See below). ! 179: Note that spacing with 'X' always writes blanks in the output record. ! 180: ! 181: II. Non-"ANSI Standard" Extensions ! 182: .PP ! 183: B is an acceptable edit control specifier. It causes return to the ! 184: default mode of blank interpretation (NULL) and is identical to BN. ! 185: This is consistent with S which returns to default sign control. ! 186: .PP ! 187: P by itself is equivalent to 0P. It resets the scale factor to the ! 188: default value, 0. ! 189: .PP ! 190: The form of the 'Ew.dEe' format specifier has been extended to 'D' also. ! 191: The form 'Ew.d.e' is allowed but is not standard. ! 192: The 'e' field specifies the minimum number of digits or spaces in the ! 193: exponent field on output. ! 194: If the value of the exponent is too large, the exponent notation 'e' ! 195: or 'd' will be dropped from the output to allow one ! 196: more character position. ! 197: If this is still not adequate, the 'e' field will be filled with ! 198: asterisks (*). The default value for 'e' is 2. ! 199: .PP ! 200: An additional form of tab control specification has been added. ! 201: The ANSI standard forms 'TRn', 'TLn', and 'Tn' are supported where n is ! 202: a positive non-zero number. If 'T' or 'nT' is specified, tabbing will ! 203: be to the next (or n-th) 8-column tab stop. ! 204: Thus columns of alphanumerics can be lined up without counting. ! 205: (See above for a description of the tabbing implementation.) ! 206: .PP ! 207: A format control specifier has been added to suppress the newline ! 208: at the end of the last record of a formatted sequential write. The ! 209: specifier is a dollar sign ($). It is constrained by the same rules ! 210: as the colon (:). It is used typically for console prompts. ! 211: For example: ! 212: ! 213: .DS ! 214: write (*, "('enter value for x: ',$)") ! 215: read (*,*) x ! 216: .DE ! 217: .PP ! 218: Radices other than 10 can be specified for formatted integer I/O ! 219: conversion. The specifier is patterned after P, the pre-scale factor for ! 220: floating point conversion. It remains in effect until another radix is ! 221: specified or format interpretation is complete. The specifier is defined ! 222: as [n]R where 2 <= n <= 36. If n is omitted, ! 223: the default decimal radix is restored. ! 224: .PP ! 225: In conjunction with the above, a sign control specifier has been added ! 226: to cause integer values to be interpreted as unsigned during output ! 227: conversion. The specifier is SU and remains in effect until another ! 228: sign control specifier is encountered, or format interpretation is ! 229: complete. Radix and 'unsigned' specifiers could be used to format ! 230: a hexadecimal dump, as follows: ! 231: ! 232: .DS ! 233: 2000 format( SU, 16R, 8I10.8) ! 234: .DE ! 235: ! 236: Note: Unsigned integer values greater than (2**30 - 1), ! 237: i.e. any signed negative value, can not be read by FORTRAN input routines. ! 238: All internal values will be output correctly. ! 239: .PP ! 240: The ANSI standard is ambiguous regarding the definition of a "print" file. ! 241: Since UNIX has no default "print" file, an additional 'form' specifier ! 242: is now recognized in the 'open' statement. ! 243: Specifying "form='print'" implies 'formatted' and enables vertical format ! 244: control for that logical unit (see above). ! 245: Vertical format control is interpreted only on sequential formatted writes ! 246: to a "print" file. ! 247: .PP ! 248: The 'inquire' statement will return 'print' in the 'FORM=' string variable ! 249: for logical units opened as "print" files. ! 250: It will return -1 for the unit number of an unconnected file. ! 251: .PP ! 252: If a logical unit is already open, an 'open' statement including the ! 253: 'form=' option or the 'blank=' option will do nothing but ! 254: re-define those options. ! 255: This instance of the 'open' statement need not include the filename, and ! 256: must not include a filename if 'unit=' refers to the standard input or outputs. ! 257: Therefore, to re-define the standard output as a "print" file, use: ! 258: ! 259: .DS ! 260: open (unit=6, form='print') ! 261: .DE ! 262: .PP ! 263: In a 'close' statement, "status='keep'" may be specified for temporary files. ! 264: This is the default for all other files. ! 265: Remember to get the file's real name, ! 266: using 'inquire', if you want to re-open it later. ! 267: .PP ! 268: List directed read has been modified to allow input of a string not enclosed ! 269: in quotes. The string must not start with a digit, and can not contain a ! 270: separator (, or /) or blank (space or tab). A newline will terminate the ! 271: string unless escaped with \\. Any string not meeting the above restrictions ! 272: must be enclosed in quotes (" or '). ! 273: .PP ! 274: Internal list-directed I/O has been implemented. During internal list reads, ! 275: bytes are consummed until the iolist is satisfied, or the 'end-of-file' ! 276: is reached. ! 277: During internal list writes, records are filled until the iolist is satisfied. ! 278: The length of an internal array element should be at least 20 bytes to ! 279: avoid logical record overflow when writing double precision values. ! 280: Internal list read was implemented to make command line decoding easier. ! 281: Internal list write should be avoided. ! 282: .bp ! 283: .ce 2 ! 284: Appendix A ! 285: I/O Library Error Messages ! 286: .PP ! 287: The following error messages are generated by the I/O library. ! 288: The error numbers are returned in the "iostat=" variable if the "err=" ! 289: return is taken. Error numbers < 100 are generated by UNIX. See the ! 290: UNIX Programmers Manual, introduction to chapter 2. ! 291: .DS ! 292: /* 100 */ "error in format" ! 293: See error message output for the location ! 294: of the error in the format. Can be caused ! 295: by more than 10 levels of nested (), or ! 296: an extremely long format statement. ! 297: ! 298: /* 101 */ "illegal unit number" ! 299: It is illegal to close logical unit 0. ! 300: Negative unit numbers are not allowed. ! 301: The upper limit is system dependent. ! 302: ! 303: /* 102 */ "formatted io not allowed" ! 304: The logical unit was opened for ! 305: unformatted I/O. ! 306: ! 307: /* 103 */ "unformatted io not allowed" ! 308: The logical unit was opened for ! 309: formatted I/O. ! 310: ! 311: /* 104 */ "direct io not allowed" ! 312: The logical unit was opened for sequential ! 313: access, or the logical record length was ! 314: specified as 0. ! 315: ! 316: /* 105 */ "sequential io not allowed" ! 317: The logical unit was opened for direct ! 318: access I/O. ! 319: ! 320: /* 106 */ "can't backspace file" ! 321: The file associated with the logical unit ! 322: can't seek. May be a device or a pipe. ! 323: ! 324: /* 107 */ "off beginning of record" ! 325: The format specified a left tab off the ! 326: beginning of the record. ! 327: ! 328: /* 108 */ "can't stat file" ! 329: The system can't return status information ! 330: about the file. Perhaps the directory is ! 331: unreadable. ! 332: ! 333: /* 109 */ "no * after repeat count" ! 334: Repeat counts in list-directed I/O must be ! 335: followed by an * with no blank spaces. ! 336: ! 337: .DE ! 338: .DS ! 339: /* 110 */ "off end of record" ! 340: A formatted write tried to go beyond the ! 341: logical end-of-record. An unformatted read ! 342: or write will also cause this. ! 343: ! 344: /* 111 */ "truncation failed" ! 345: The truncation of external sequential files ! 346: on 'close', 'backspace', or 'rewind' tries ! 347: to do a copy. It failed. Perhaps the temp ! 348: file couldn't be created. ! 349: ! 350: /* 112 */ "incomprehensible list input" ! 351: List input has to be just right. ! 352: ! 353: /* 113 */ "out of free space" ! 354: The library dynamically creates buffers for ! 355: internal use. You ran out of memory for this. ! 356: Your program is too big! ! 357: ! 358: /* 114 */ "unit not connected" ! 359: The logical unit was not open. ! 360: ! 361: /* 115 */ "read unexpected character" ! 362: Certain format conversions can't tolerate ! 363: non-numeric data. Logical data must be ! 364: T or F. ! 365: ! 366: /* 116 */ "blank logical input field" ! 367: ! 368: /* 117 */ "'new' file exists" ! 369: You tried to open an existing file with ! 370: "status='new'". ! 371: ! 372: /* 118 */ "can't find 'old' file" ! 373: You tried to open a non-existent file ! 374: with "status='old'". ! 375: ! 376: /* 119 */ "unknown system error" ! 377: Shouldn't happen, but ..... ! 378: (Send me a documented example.) ! 379: ! 380: /* 120 */ "requires seek ability" ! 381: Direct access requires seek ability. ! 382: Sequential unformatted I/O requires seek ! 383: ability on the file due to the special ! 384: data structure required. Tabbing left ! 385: also requires seek ability. ! 386: ! 387: /* 121 */ "illegal argument" ! 388: Certain arguments to 'open', etc. will be ! 389: checked for legitimacy. Often only non- ! 390: default forms are looked for. ! 391: ! 392: /* 122 */ "negative repeat count" ! 393: The repeat count on list directed input ! 394: must be a positive integer. ! 395: .DE
This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.