{"id":425,"date":"2011-06-23T19:31:36","date_gmt":"2011-06-23T19:31:36","guid":{"rendered":"http:\/\/craftydba.com\/?p=425"},"modified":"2024-02-17T14:25:47","modified_gmt":"2024-02-17T14:25:47","slug":"fixed-formatted-text-files","status":"publish","type":"post","link":"https:\/\/craftydba.com\/?p=425","title":{"rendered":"Fixed Formatted Text Files"},"content":{"rendered":"

The invention of a fixed formatted text (flat) file layout started with IBM<\/a> in the 1960’s. Data sets on the mainframe could be stored in both fixed and variable length records.<\/p>\n

A flat file<\/a> is defined as having one record of data per row that is ended with a new line. Each field inside the record is represented by a fixed number of characters.<\/p>\n

While flat files can have either ASCII<\/a> or EBCDIC<\/a> encoding, I will be exploring the former. Another generalization of this format is to store numbers in their machine form, binary coding. I will not be talking about this option today.<\/p>\n

I will be using the read and write text file classes created earlier to implement a solution for storing data on the first five Presidents of the United States.<\/p>\n

The table below summarizes the methods and properties of the classes.<\/p>\n\n\n\n\n\n\n\n\n\n\n
OpenDataFile()<\/td>\nRead & Write<\/td>\n<\/tr>\n
CloseDataFile()<\/td>\nRead & Write<\/td>\n<\/tr>\n
PushData()<\/td>\nWrite<\/td>\n<\/tr>\n
PullData()<\/td>\nRead<\/td>\n<\/tr>\n
PullAllData()<\/td>\nRead<\/td>\n<\/tr>\n
RemoveFile()<\/td>\nWrite<\/td>\n<\/tr>\n
FileExists()<\/td>\nRead<\/td>\n<\/tr>\n
EOF<\/td>\nRead<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/P><\/p>\n

 <\/P><\/p>\n

 <\/P><\/p>\n

 <\/P><\/p>\n

 <\/P><\/p>\n

 <\/P><\/p>\n

The trick to this format is to use a string buffer and to place the fields at the correct positions. All numeric data has to be saved text which may or may not cause lose of percision. I wrote the following helper functions to solve this buffer manipulation.<\/p>\n

\nThe “PackField” helper function packages a variable length string into a fixed one. Any null issues are avoided by appending a empty string at the start of the expression.<\/p>\n

\r\nPublic Function PackField(strData, intSize)\r\n   PackField = mid(\"\" & strData & Space(intSize), 1, intSize)\r\nEnd Function\r\n<\/pre>\n
 <\/p>\n
The “UnpackField” helper function chops off the field at the start of the string and returns it.  The orginal string is modified to remove from the record.<\/p>\n
\r\nPublic Function UnpackField(strData, intLength)\r\n    If len(strData) < intLength Then\r\n        UnpackField = strData\r\n    Else\r\n        UnpackField = Mid(strData, 1, intLength)\r\n        strData = Mid(strData, intLength+1)\r\n    End If\r\nEnd Function\r\n<\/pre>\n
 <\/p>\n
In summary, writing to and reading from fixed formatted text files is very easy.  You might bump into this format when exchanging data with clients that use the IBM mainframe.<\/p>\n
The table below has started code that you can use in your next Visual Basic (VB) Script.<\/p>\n\n\n\n\n\n\n\n\n\n\n
mod-write-text-file.vbs<\/a>\n<\/td>\nWrite Text File Class<\/td>\n<\/tr>\n
mod-read-text-file.vbs<\/a>\n<\/td>\nRead Text File Class<\/td>\n<\/tr>\n
tst-write-flat-file.vbs<\/a>\n<\/td>\nWrite Flat File Program<\/td>\n<\/tr>\n
tst-read-flat-file.vbs<\/a>\n<\/td>\nRead Flat File Program<\/td>\n<\/tr>\n
write-flat.cmd<\/a>\n<\/td>\nWrite Batch File<\/td>\n<\/tr>\n
read-flat.cmd<\/a>\n<\/td>\nRead Batch File<\/td>\n<\/tr>\n
presidents<\/a>\n<\/td>\nPresidents Flat File<\/td>\n<\/tr>\n
\nflat-file-output<\/a>\n<\/td>\nRead Program Output<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n","protected":false},"excerpt":{"rendered":"
The invention of a fixed formatted text (flat) file layout started with IBM in the 1960’s. Data sets on the mainframe could be stored in both fixed and variable length records. A flat file is defined as having one record of data per row that is ended with a new line. Each field inside the record is represented by a fixed number of characters. While flat files can have either ASCII or EBCDIC encoding, I will be exploring the former. Another generalization of this format is to store numbers in…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[26,27,12,15,13],"class_list":["post-425","post","type-post","status-publish","format-standard","hentry","category-other","tag-fixed-format","tag-flat-files","tag-free-code","tag-john-f-miner-iii","tag-vb-script-2"],"_links":{"self":[{"href":"https:\/\/craftydba.com\/index.php?rest_route=\/wp\/v2\/posts\/425","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/craftydba.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/craftydba.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/craftydba.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/craftydba.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=425"}],"version-history":[{"count":0,"href":"https:\/\/craftydba.com\/index.php?rest_route=\/wp\/v2\/posts\/425\/revisions"}],"wp:attachment":[{"href":"https:\/\/craftydba.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=425"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/craftydba.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=425"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/craftydba.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=425"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}