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Convert tabs to spaces in tcl??

Posted on 2008-11-11
Medium Priority
Last Modified: 2013-12-21
Using tcl, I'm reading through a file generated by a report-writer. There are some records that have tabs in them, some don't. I need to parse out the fields (columns in the report) positionally. The problem is using string range or crange views the \t in the records as single characters

I tried doing
regsub -all $rec \t "     " rec
but since the amount of whitespace in a tab is not static, I was getting undesired results.

Example of report line:
10/27/08                   801062347       801062347                .00    Charge                  70.99       N
Corresponding example of octal display from the report file:
0001460   \r  \n   1   0   /   2   7   /   0   8                  \t  \t
0001500                8   0   1   0   6   2   3   4   7  \t
0001520    8   0   1   0   6   2   3   4   7  \t  \t                   .
0001540    0   0                   C   h   a   r   g   e  \t  \t
0001560        7   0   .   9   9                               N  \r  \n

I'd prefer to handle this in the tcl script but if necessary, I suppose I can manipulate the file using ksh beforehand, although I'm not sure how I would do that either.

Any ideas?
Question by:sjmont
LVL 24

Expert Comment

ID: 22939148
Well  this would be a very big suprise. The tab-width does not change. At least this would be the first time I heard of it. As you can see however there are quite a few \t in there. I'd probably go another route just split the line into pieces limited by whitespace. Or you can use another regular expression
which matches the given text better


Expert Comment

ID: 23315587
Can this be used:
% set conv_rec [lrang $rec 0 6]
10/27/08 801062347 801062347 .00 Charge 70.99 N

Author Comment

ID: 23316435
Yes, that's a valid thought. I guess I should have mentioned that the reason I was parsing the data positionally was because there sometimes is a field missing from the record, for example:


11/01/08                   801000349       801000349                .00    Charge                  63.00       N

11/01/08    00566317       801000886       801000886                .00    Charge                  11.25       N

So in such a case using a list would offset the data in the list elements
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Expert Comment

ID: 23316960
Does defining start and end of each field, then use "string range" work for you? For example:
set dt_start 0
set dt_end 7
set trans_start 8
set trans_end 19
set dt [string range $rec $dt_start $dt_end]
set trans_nu [string range $rec $trans_start $trans_end]

Accepted Solution

leh327 earned 2000 total points
ID: 23317778

Since each field has its own length, replacing each "\t" with a constant number of space is giving you incorrect result, right?

Do you already know how many spaces to replace "\t" for each field?

od -t a yourfile.txt
should have shown how many spaces should be used to replace one "\t" for each field.

For example:
When trans_nu comes back missing or doesn't match some rule, a positional replacing "\t\t" with "    \t" (four spaces)

set conv_rec [join "{[regsub -all \t\t [string range $rec $trans_start $trans_end] "    \t"]} {[string range $rec $cus_start end]}" ""]


Expert Comment

ID: 25983545
If I understand your quest correctly, you want to replace tabs with spaces while keeping the same "positioning"  as the tabs produce in a terminal?
The reason for this being that you intend to match the position of the headers with the data fields, or something like that? I think that is also what has been suggested above kind of?

The attached proceedure could perhaps be of some assistance with replacing tabs with space at least. Probably very slow, but might be good enough for small amounts of data, or you can just use the idea, and write a better performing version :-)
It simply walks through the original string one char at a time, and if there is a tab at the position it will be substituted with enough spaces to pad up to the next tab-stop (column width defined by the tabstop variable).
proc tab2space { str } { 
        set tabstop 8 
        set n 0
        set nspc 0 
        set strlen [string length $str]
        while { $n < $strlen } {
                set c [string index $str $n]
                if { "$c" == "\t" } {
                        set nn [expr $n + $nspc]
                        set spaces [expr $tabstop - ( $nn % $tabstop )]
                        incr nspc [expr $spaces - 1]
                        append newstr "[string repeat " " $spaces]"
                } else {
                        append newstr $c
                incr n
        return "$newstr"

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