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6.12 General Utility Subroutines

The following utility subroutines may be useful for certain applications:

Return the starting byte address of the CHDU and the next HDU.

        FTGHAD(iunit, > curaddr, nextaddr)

Convert a character string to uppercase (operates in place).


Compare the input template string against the reference string to see if they match. The template string may contain wildcard characters: '*' will match any sequence of characters (including zero characters) and '?' will match any single character in the reference string. The '#' character will match any consecutive string of decimal digits (0 - 9). If CASESN = .true. then the match will be case sensitive. The returned MATCH parameter will be .true. if the 2 strings match, and EXACT will be .true. if the match is exact (i.e., if no wildcard characters were used in the match). Both strings must be 68 characters or less in length.

        FTCMPS(str_template, string, casesen, > match, exact)

Test that the keyword name contains only legal characters: A-Z,0-9, hyphen, and underscore.

        FTTKEY(keyword, > status)

Test that the keyword record contains only legal printable ASCII characters

        FTTREC(card, > status)

Test whether the current header contains any NULL (ASCII 0) characters. These characters are illegal in the header, but they will go undetected by most of the CFITSIO keyword header routines, because the null is interpreted as the normal end-of-string terminator. This routine returns the position of the first null character in the header, or zero if there are no nulls. For example a returned value of 110 would indicate that the first NULL is located in the 30th character of the second keyword in the header (recall that each header record is 80 characters long). Note that this is one of the few FITSIO routines in which the returned value is not necessarily equal to the status value).

        FTNCHK(unit, > status)

Parse a header keyword record and return the name of the keyword and the length of the name. The keyword name normally occupies the first 8 characters of the record, except under the HIERARCH convention where the name can be up to 70 characters in length.

        FTGKNM(card, > keyname, keylength, staThe '\#' character will match any consecutive string
    of decimal digits (0 - 9). tus)

Parse a header keyword record. This subroutine parses the input header record to return the value (as a character string) and comment strings. If the keyword has no value (columns 9-10 not equal to '= '), then the value string is returned blank and the comment string is set equal to column 9 - 80 of the input string.

        FTPSVC(card, > value,comment,status)

Construct a properly formated 80-character header keyword record from the input keyword name, keyword value, and keyword comment strings. Hierarchical keyword names (e.g., "ESO TELE CAM") are supported. The value string may contain an integer, floating point, logical, or quoted character string (e.g., "12", "15.7", "T", or "'NGC 1313'").

        FTMKKY(keyname, value, comment, > card, status)

Construct a sequence keyword name (ROOT + nnn). This subroutine appends the sequence number to the root string to create a keyword name (e.g., 'NAXIS' + 2 = 'NAXIS2')

        FTKEYN(keyroot,seq_no, > keyword,status)

Construct a sequence keyword name (n + ROOT). This subroutine concatenates the sequence number to the front of the root string to create a keyword name (e.g., 1 + 'CTYP' = '1CTYP')

        FTNKEY(seq_no,keyroot, > keyword,status)

Determine the datatype of a keyword value string. This subroutine parses the keyword value string (usually columns 11-30 of the header record) to determine its datatype.

        FTDTYP(value, > dtype,status)

Return the class of input header record. The record is classified into one of the following categories (the class values are defined in fitsio.h). Note that this is one of the few FITSIO routines that does not return a status value.

       Class  Value             Keywords
                     GROUPS, PCOUNT, GCOUNT, END
                     XTENSION, TFIELDS, TTYPEn, TBCOLn, TFORMn, THEAP,
                     and the first 4 COMMENT keywords in the primary array
                     that define the FITS format.
  TYP_CMPRS_KEY  20  The experimental keywords used in the compressed
                     image format ZIMAGE, ZCMPTYPE, ZNAMEn, ZVALn,
  TYP_DIM_KEY    50  TDIMn
                     CDj_is, PVj_ms, LONPOLEs, LATPOLEs
                     TCTYPn, TCTYns, TCUNIn, TCUNns, TCRVLn, TCRVns, TCRPXn,
                     TCRPks, TCDn_k, TCn_ks, TPVn_m, TPn_ms, TCDLTn, TCROTn
                     jCTYPn, jCTYns, jCUNIn, jCUNns, jCRVLn, jCRVns, iCRPXn,
                     iCRPns, jiCDn,  jiCDns, jPVn_m, jPn_ms, jCDLTn, jCROTn
                     (i,j,m,n are integers, s is any letter)
  TYP_COMM_KEY   130 COMMENT, HISTORY, (blank keyword)
  TYP_USER_KEY   150 all other keywords

         class = FTGKCL (char *card)

Parse the 'TFORM' binary table column format string. This subroutine parses the input TFORM character string and returns the integer datatype code, the repeat count of the field, and, in the case of character string fields, the length of the unit string. The following datatype codes are returned (the negative of the value is returned if the column contains variable-length arrays):

                Datatype                DATACODE value
                bit, X                   1
                byte, B                 11
                logical, L              14
                ASCII character, A      16
                short integer, I        21
                integer, J              41
                real, E                 42
                double precision, D     82
                complex                 83
                double complex          163

        FTBNFM(tform, > datacode,repeat,width,status)

Parse the 'TFORM' keyword value that defines the column format in an ASCII table. This routine parses the input TFORM character string and returns the datatype code, the width of the column, and (if it is a floating point column) the number of decimal places to the right of the decimal point. The returned datatype codes are the same as for the binary table, listed above, with the following additional rules: integer columns that are between 1 and 4 characters wide are defined to be short integers (code = 21). Wider integer columns are defined to be regular integers (code = 41). Similarly, Fixed decimal point columns (with TFORM = 'Fw.d') are defined to be single precision reals (code = 42) if w is between 1 and 7 characters wide, inclusive. Wider 'F' columns will return a double precision data code (= 82). 'Ew.d' format columns will have datacode = 42, and 'Dw.d' format columns will have datacode = 82.

        FTASFM(tform, > datacode,width,decimals,status)

Calculate the starting column positions and total ASCII table width based on the input array of ASCII table TFORM values. The SPACE input parameter defines how many blank spaces to leave between each column (it is recommended to have one space between columns for better human readability).

        FTGABC(tfields,tform,space, > rowlen,tbcol,status)

Parse a template string and return a formatted 80-character string suitable for appending to (or deleting from) a FITS header file. This subroutine is useful for parsing lines from an ASCII template file and reformatting them into legal FITS header records. The formatted string may then be passed to the FTPREC, FTMCRD, or FTDKEY subroutines to append or modify a FITS header record.

        FTGTHD(template, > card,hdtype,status)
The input TEMPLATE character string generally should contain 3 tokens: (1) the KEYNAME, (2) the VALUE, and (3) the COMMENT string. The TEMPLATE string must adhere to the following format:

The KEYNAME token must begin in columns 1-8 and be a maximum of 8 characters long. If the first 8 characters of the template line are blank then the remainder of the line is considered to be a FITS comment (with a blank keyword name). A legal FITS keyword name may only contain the characters A-Z, 0-9, and '-' (minus sign) and underscore. This subroutine will automatically convert any lowercase characters to uppercase in the output string. If KEYNAME = 'COMMENT' or 'HISTORY' then the remainder of the line is considered to be a FITS COMMENT or HISTORY record, respectively.

The VALUE token must be separated from the KEYNAME token by one or more spaces and/or an '=' character. The datatype of the VALUE token (numeric, logical, or character string) is automatically determined and the output CARD string is formatted accordingly. The value token may be forced to be interpreted as a string (e.g. if it is a string of numeric digits) by enclosing it in single quotes. If the value token is a character string that contains 1 or more embedded blank space characters or slash ('/') characters then the entire character string must be enclosed in single quotes.

The COMMENT token is optional, but if present must be separated from the VALUE token by a blank space or a '/' character.

One exception to the above rules is that if the first non-blank character in the template string is a minus sign ('-') followed by a single token, or a single token followed by an equal sign, then it is interpreted as the name of a keyword which is to be deleted from the FITS header.

The second exception is that if the template string starts with a minus sign and is followed by 2 tokens then the second token is interpreted as the new name for the keyword specified by first token. In this case the old keyword name (first token) is returned in characters 1-8 of the returned CARD string, and the new keyword name (the second token) is returned in characters 41-48 of the returned CARD string. These old and new names may then be passed to the FTMNAM subroutine which will change the keyword name.

The HDTYPE output parameter indicates how the returned CARD string should be interpreted:

        hdtype                  interpretation
        ------           -------------------------------------------------
           -2            Modify the name of the keyword given in CARD(1:8)
                         to the new name given in CARD(41:48)

           -1            CARD(1:8) contains the name of a keyword to be deleted
                         from the FITS header.

            0            append the CARD string to the FITS header if the
                         keyword does not already exist, otherwise update
                         the value/comment if the keyword is already present
                         in the header.

            1            simply append this keyword to the FITS header (CARD
                         is either a HISTORY or COMMENT keyword).

            2            This is a FITS END record; it should not be written
                         to the FITS header because FITSIO automatically
                         appends the END record when the header is closed.
EXAMPLES: The following lines illustrate valid input template strings:

      INTVAL 7 This is an integer keyword
      RVAL           34.6   /     This is a floating point keyword
      EVAL=-12.45E-03  This is a floating point keyword in exponential notation
      lval F This is a boolean keyword
                  This is a comment keyword with a blank keyword name
      SVAL1 = 'Hello world'   /  this is a string keyword
      SVAL2  '123.5'  this is also a string keyword
      sval3  123+  /  this is also a string keyword with the value '123+    '
      # the following template line deletes the DATE keyword
      - DATE
      # the following template line modifies the NAME keyword to OBJECT

Parse the input string containing a list of rows or row ranges, and return integer arrays containing the first and last row in each range. For example, if rowlist = "3-5, 6, 8-9" then it will return numranges = 3, rangemin = 3, 6, 8 and rangemax = 5, 6, 9. At most, 'maxranges' number of ranges will be returned. 'maxrows' is the maximum number of rows in the table; any rows or ranges larger than this will be ignored. The rows must be specified in increasing order, and the ranges must not overlap. A minus sign may be use to specify all the rows to the upper or lower bound, so "50-" means all the rows from 50 to the end of the table, and "-" means all the rows in the table, from 1 - maxrows.

    FTRWRG(rowlist, maxrows, maxranges, >
           numranges, rangemin, rangemax, status)

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Next: 7. The CFITSIO Iterator Up: 6. Advanced Interface Subroutines Previous: 6.11 Date and Time   Contents