ftverify - Verify that a FITS file conforms to the FITS Standard.


ftverify infile


ftverify @filelist


This task reads a FITS file (or a list of FITS files) and verifies that the format conforms to the specifications of the FITS Standard "Definition of the Flexible Image Transport System (FITS)", Version 3.0, available on line at The following error or warning conditions will be flagged:


     - Mandatory keyword not present or out of order
     - Mandatory keyword has wrong datatype or illegal value
     - END header keyword is not present
     - Sum of table column widths is inconsistent with NAXIS1 value
     - BLANK keyword present in image with floating-point datatype
     - TNULLn keyword present for floating-point binary table column
     - Bit column has non-zero fill bits or is not left adjusted(*)
     - ASCII TABLE column contains illegal value inconsistent with TFORMn(*)
     - Address to a variable length array not within the data heap(*)
     - Extraneous bytes in the FITS file following the last HDU


     - Mandatory keyword values not expressed in fixed format
     - Mandatory keyword duplicated elsewhere in the header
     - Header contains illegal ASCII character (not ASCII 32 - 126)
     - Keyword name contains illegal character
     - Keyword value field has illegal format
     - Value and comment fields not separated by a slash character
     - END keyword not filled with blanks in columns 9 - 80
     - Reserved keyword with wrong datatype or illegal value
     - XTENSION keyword in the primary array
     - Column related keyword (TFIELDS, TTYPEn,TFORMn, etc.) in an image
     - SIMPLE, EXTEND, or BLOCKED keyword in any extension
     - BSCALE, BZERO, BUNIT, BLANK, DATAMAX, DATAMIN keywords in a table
     - Table WCS keywords (TCTYPn, TCRPXn, TCRVLn, etc.) in an image
     - TDIMn or THEAP keyword in an ASCII table
     - TBCOLn keyword in a Binary table
     - THEAP keyword in a binary table that has PCOUNT = 0
     - XTENSION, TFORMn, TDISPn or TDIMn value contains leading space(s)
     - WCSAXES keyword appears after other WCS keywords
     - Index of any WCS keyword (CRPIXn, CRVALn, etc.) greater than
       value of WCSAXES
     - Index of any table column descriptor keyword (TTYPEn, TFORMn,
       etc.) greater than value of TFIELDS
     - TSCALn or TZEROn present for an ASCII, logical, or Bit column
     - TDISPn value is inconsistent with the column datatype
     - Length of a variable length array greater than the maximum
       length as given by the TFORMn keyword
     - ASCII table floating-point column value does not have decimal point(*)
     - ASCII table numeric column value has embedded space character
     - Logical column contains illegal value not equal to 'T', 'F', or 0(*)
     - Character string column contains non-ASCII text character(*)
     - Header fill bytes not all blanks (**)
     - Data fill bytes not all blanks in ASCII tables or all zeros
       in any other type of HDU (**)
     - Gaps between defined ASCII table columns contain characters with
       ASCII value > 127  (**)


     - SIMPLE = F
     - Presence of deprecated keywords BLOCKED or EPOCH
     - 2 HDUs have identical EXTNAME and EXTVER values
     - BSCALE or TSCALn value = 0.
     - BLANK OR TNULLn value exceeds the legal range
     - TFORMn has 'rAw' format and r is not a multiple of w
     - DATE = 'dd/mm/yy' and yy is less than 10 (Y2K problem??)
     - Index of any WCS keyword (CRPIXn, CRVALn, etc.) greater than
       value of NAXIS, if the WCSAXES keyword is not present
     - Duplicated keyword (except COMMENT, HISTORY, blank, etc.)
     - Column name (TTYPEn) does not exist or contains characters
       other than letter, digit and underscore
     - Binary table has PCOUNT > 0, but no variable-length array columns
     - Calculated checksum inconsistent with CHECKSUM or DATASUM
     - The HEASARC long string keyword convention is used without the
       recommended LONGSTRN keyword (****)

        (*) only checked when "testdata" is 'Yes'
       (**) only checked when "testdata" and "testfill" are 'Yes'
      (***) only checked when "testdata" and "tchksum" are 'Yes'
     (****) only checked when the "heasarc" is 'Yes'
Every HDU in the FITS file is checked in turn until the end of file is detected. A summary table is printed to the terminal (or to an optional output file) showing the structure of the FITS file. A listing of all the header keywords may also be produced. At the end of the verification, a summary of the warnings and errors in each HDU are printed.

The amount of information that is displayed can be controlled with the prhead, prstat and errreport parameters.


infile [filename]
Name of the FITS file to be verified. If this starts with "@" then it is assumed to be an ascii file containing a list of files (one filename per line) to be verified.

(outfile = "STDOUT" [filename]
Name of output verification report file. If outfile is blank or = 'STDOUT' then the results will be written to the standard output device (usually the user's terminal) rather than to a file. If preceded by a !, an existing file of the same name will be overwritten.

(prhead = no) [boolean]
Should a listing of the header keywords be included in the verification report?

(prstat = yes) [boolean]
Should a detailed verification report be produced? If 'NO', then only a 1-line pass/fail message will be printed. In this case, the OUTFILE and PRHEAD parameters are ignored.

(errreport = "w") [string]
The first letter of this parameter controls the level of error reporting, as follows:
's' for "severe" - only report the most severe errors
'e' for "errors" - report all errors
'w' for "warnings" - report warnings as well as all errors
Any other letter will be treated the same as the default 'w'.

(testdata = yes) [boolean]
Should data values be read and verified? If set = YES, then all the columns in ASCII tables and the character string (A), logical (L) and bit (X) columns in binary tables will be read and verified. Image arrays, and the numeric type columns in binary tables are not read because it is impossible for these datatypes to have an illegal value. Setting testdata = No may improved the execution speed of the task at the expense of doing a less rigorous verification of the FITS file.

(tchksum = yes) [boolean]
Should the checksum of the header and data be tested? The tests are performed only if the CHECKSUM and DATASUM keywords exist.

(testfill = yes) [boolean]
Should the bytes in the fill area be verified? The fill areas are defined as a) gaps between ASCII table columns, b) bytes following the END card within the same FITS 2880-byte block and c) bytes following the end of the data within the same FITS 2880-byte block. The values of these fill bytes should have no effect on the data in the FITS file, nevertheless, the FITS standard requires that they have a zero, or in some cases, an ASCII blank value. Invalid fill values may be an indication of more serious problems in the file.

(heasarc = yes) [boolean]
Should the HEASARC conventions be verified? The HEASARC conventions go beyond the offical NOST FITS Standard. At the present time the only significant HEASARC conventions are that column names must begin with a letter and be unique within the first 16 characters.

(numerrs = 0 ) [int]
Number of the errors found in the verification of the FITS file. For multiple input files, this is the accumulated number of errors over all the files.

(numwrns = 0 ) [int]
Number of the warnings found in the verification of the FITS file. For multiple input files, this is the accumulated number of warnings over all the files.

(clobber = NO) [boolean]
If the output file already exists, then setting "clobber = yes" will cause it to be overwritten.


1. Verify the contents of the FITS file 'test.fits'.

      ftverify test.fits
2. Verify the FITS file 'test.fits' and print all the header keywords:

      ftverify test.fits prhead=yes
3. Check the FITS file 'test.fits' for only the most severe errors, ignoring less significant errors and warnings:

      ftverify test.fits errreport=s
4. Verify a list of FITS files. In this case 'filelist.txt' is an ASCII text file containing the list of files to be verified, one per line. Since prstat=no, only a single line of output will be written per file, stating whether the file passed or failed the verification.

      ftverify @filelist.txt prstat=no


ftlist, ftchecksum ftstat

"Definition of the Flexible Image Transport System (FITS)", Version 3.0, available on line at

The design of this task is based on the fverify in the ftools package.


October 2010