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Top Forums UNIX for Advanced & Expert Users Should I say "field 8" or "column 8" in this case? Post 302784755 by Don Cragun on Saturday 23rd of March 2013 01:21:38 AM
Old 03-23-2013
Quote:
Originally Posted by hanson44
Yes, I think the sort syntax reinforces what I was trying to say. "sort -t, -k 8 fields.txt" sorts "field 8". The sort man page refers to "field separator" and "field number" and --field-separator. "column" is not even mentioned on the sort man page.

For the position within a field, both sort and cut use "character" instead of "column". In other words, cut says --characters where I would have said --columns. To me "characters" is confusing, as could be interpreted to be "--characters=ABC" as if looking for those "characters". The man pages says "select only these characters". Why did they choose --characters instead of --columns for the option name?

Of course, nobody is going to change the option name at this point. I suppose they could at least improve the cut man page, to say "select only these character positions".
If you have a tab character, it may occupy one or more columns. If you have a backspace character, that character and the character it follows may occupy only one column. If you are looking at a Kanji character, a single character may occupy two columns. That is why we chose character rather than column for the tag associated with the -c option to sort.

The cut utility does not perform cuts based on the columns in which characters will be displayed. It can perform cuts based on the number of bytes (-b), the number of characters (-c), or the number of fields (-f). There is no option to cut the characters or bytes that will occupy a particular range of column positions (such as recognizing that the three character sequence <a><backspace><underline> immediately following a <newline> character will all occupy output column number one on some output devices). And the way the sequence of characters <a><tab><backspace><c> translates into output columns may vary considerably based not only on the position within a line where it appears but also on the software or hardware that is interpreting that sequence. Does the <backspace> character backspace over the previous output column or over the previous character (<tab> in this case)? What does the <backspace> character do when it is the first character on a line? Again, counting characters provides a clearly defined operation. If we had used output columns instead of characters (or bytes), the behavior required would not match any known existing implementation of the cut utility.

When using a fixed width character set, rows and columns are solid concepts on a CRT, typewriter, or printer and also when talking about entries in a table in a spreadsheet. Columns are much less precise when talking about the contents of a text file.

Characters, on the other hand, are explicitly defined by the LC_CTYPE category of the current locale.
 

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COLRM(1)						    BSD General Commands Manual 						  COLRM(1)

NAME
colrm -- remove columns from a file SYNOPSIS
colrm [start [stop]] DESCRIPTION
The colrm utility removes selected columns from the lines of a file. A column is defined as a single character in a line. Input is read from the standard input. Output is written to the standard output. If only the start column is specified, columns numbered less than the start column will be written. If both start and stop columns are spec- ified, columns numbered less than the start column or greater than the stop column will be written. Column numbering starts with one, not zero. Tab characters increment the column count to the next multiple of eight. Backspace characters decrement the column count by one. ENVIRONMENT
The LANG, LC_ALL and LC_CTYPE environment variables affect the execution of colrm as described in environ(7). EXIT STATUS
The colrm utility exits 0 on success, and >0 if an error occurs. SEE ALSO
awk(1), column(1), cut(1), paste(1) HISTORY
The colrm command appeared in 3.0BSD. BSD
August 4, 2004 BSD
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