tcl, tcl equivalent of NR in awk

tcl equivalent of NR in awk

Author	Message
Sriram Kishore Rallabhand #1 / 5	tcl equivalent of NR in awk Hi I'm new to this. And I have convert an awk script to tcl script. I have to read some arbitrary lines of a particular file and print it to another file. The reading has to be done by picking some specific lines here and there, and back and forth, and reading off some fields in the line into another file. awk does this by using the NR command. I wanted to find out if there is an equivalent of NR in tcl, instead of using many 'if' loops, which may take a long cpu time. Also if there's no such equivalent, what is the best way to do this. Please help Bye Sriram ***************************************************************************** Georgia Institute of Technology, Phone: Office (404) 894-0318 Atlanta Georgia, 30332 Resi (404) 872-1294 *****************************************************************************
Wed, 07 May 2003 03:00:00 GMT

Bob Techenti #2 / 5	tcl equivalent of NR in awk Quote: > Hi > I'm new to this. And I have convert an awk script to tcl script. I have > to read some arbitrary lines of a particular file and print it to another > file. The reading has to be done by picking some specific lines here and > there, and back and forth, and reading off some fields in the line into > another file. awk does this by using the NR command. I wanted to > find out if there is an equivalent of NR in tcl, instead of using many > 'if' loops, which may take a long cpu time. > Also if there's no such equivalent, what is the best way to do this. > Please help Since the awk NR is the record number, I assume that you're trying to get specific lines from a file by their line number. The "Tcl way" to do that, for small files that can be read entirely into memory, is to read the data in one fell swoop, then split it into a list, like this: set filename "myfile.dat" set fp [open $filename "r"] set data [split [read $fp [file size $filename]] "\n"] close $fp Then the variable 'data' contains a list of lines. You can get at a specific line by using the list index function: set p [lindex $data 122] puts "line 122: '$p'" If the original data file is very large, then you're stuck reading each line in a loop. If you're planning on matching lines, then look at the regular expression man pages. This is much more powerful than awk could ever hope to be. Bob -- Mayo Foundation (507) 284-2702 Rochester MN, 55905 USA http://www.mayo.edu/sppdg/sppdg_home_page.html
Fri, 09 May 2003 03:00:00 GMT

Donal K. Fellow #3 / 5	tcl equivalent of NR in awk Quote: >I'm new to this. And I have convert an awk script to tcl script. I have >to read some arbitrary lines of a particular file and print it to another >file. The reading has to be done by picking some specific lines here and >there, and back and forth, and reading off some fields in the line into >another file. awk does this by using the NR command. I wanted to >find out if there is an equivalent of NR in tcl, instead of using many >'if' loops, which may take a long cpu time. >Also if there's no such equivalent, what is the best way to do this. Its been a while since I fiddled with AWK; NR is the number of lines in the file? If so and your data file is not too big (a condition which depends very much on the size of computer you're using) then you are probably best off loading the whole file into Tcl at once and processing it in memory - [for] loops are way cheaper than system calls. set f [open $filename r] set lines [split [read $f [file size $filename]] "\n"] close $f set NR [llength $lines]; # Make things easy for yourself! :^) If the amount of data you are dealing with is "large" then you'll need a more creative solution. But that's a big topic. Donal. -- Donal K. Fellows (at home) -- FOOLED you! Absorb EGO SHATTERING impulse rays, polyester poltroon!! (WARNING: There is precisely one error in this message.)
Fri, 09 May 2003 03:00:00 GMT

Donal K. Fellow #4 / 5	tcl equivalent of NR in awk Quote: >If the original data file is very large, then you're stuck reading each >line in a loop. You can also do some tricks with [seek] provided you've got a real file. Quote: >If you're planning on matching lines, then look at the >regular expression man pages. This is much more powerful than awk could >ever hope to be. I thought AWK could do regexp stuff (though its RE language is not as rich as that of recent versions of Tcl.) The real advantage of a language like Tcl over AWK comes when you throw in multiple files (or extensions. :^) Donal. -- Donal K. Fellows (at home) -- FOOLED you! Absorb EGO SHATTERING impulse rays, polyester poltroon!! (WARNING: There is precisely one error in this message.)
Fri, 09 May 2003 03:00:00 GMT

lvir.. #5 / 5	tcl equivalent of NR in awk In case anyone is interested, I started a <URL: http://purl.org/thecliff/tcl/wiki/> page for the topic of awk like solutions in Tcl - I hope people will add the idioms that they have found make Tcl more powerful than awk. See http://mini.net/cgi-bin/wikit/1063.html for details. -- "See, he's not just anyone ... he's my son." Mark Schultz Even if explicitly stated to the contrary, nothing in this posting should be construed as representing my employer's opinions.
Sat, 10 May 2003 03:00:00 GMT

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