egghelp/eggheads community

Writing, reading and deleting data from a file

2009-02-18T16:29:40-04:00

thanks guys, you were a great help!!!

Statistics: Posted by Fill — Wed Feb 18, 2009 4:29 pm

Writing, reading and deleting data from a file

2009-02-14T20:53:49-04:00

http://wiki.tcl.tk/17396 Would be a good place to start, however, if you look in the TCL FAQ part of the forum. There is a thread dedicated to File stuff

Statistics: Posted by TCL_no_TK — Sat Feb 14, 2009 8:53 pm

Writing, reading and deleting data from a file

2009-02-14T20:51:44-04:00

I tend to prefer to keep a complete copy of a file's contents in memory and write it whenever a change is made. Perhaps something like the following code :-

Code:

# call this proc to read the file whatever.txtproc pReadFile {} {    global vFileData    if {[file exists whatever.txt]} {        set id [open whatever.txt r]        set vFileData [split [read -nonewline $id] \n]        close $id    } else {        # handle file doesn't exist    }    return 0}     # call this proc to write the file whatever.txt# the file is first created if it doesn't exist or truncated if it doesproc pWriteFile {} {    global vFileData    if {[info exists vFileData]} {        set id [open whatever.txt w]        puts $id [join $vFileData \n]        close $id    } else {        # handle no data    }    return 0}# call this proc with 1 argument (text to search for in vFileData and if found remove that list item)# only the first list item matching *txt* will be removed# this proc calls pWriteFile if a deletion was madeproc pDeleteLine {txt} {    global vFileData    if {[info exists vFileData]} {        if {[set idx [lsearch $vFileData *$txt*]] != -1} {            set vFileData [lreplace $vFileData $idx $idx]            pWriteFile        } else {            # handle not found        }    } else {        # handle no data    }    return 0}# call this proc with 1 argument (text to add as a list item to vFileData)# this proc calls pWriteFile after the text is appended as a list itemproc pAddLine {txt} {    global vFileData    lappend vFileData $txt    pWriteFile    return 0}

Workable, as long as the data isn't a monstrous size.

Statistics: Posted by arfer — Sat Feb 14, 2009 8:51 pm

Writing, reading and deleting data from a file

2009-02-14T20:51:18-04:00

Simply put, you can't.

But... what you can do, is read the whole file into memory, and manipulate the content there. Then you either remove the old file and create a new (empty) one, or reopen the file with the TRUNC option (truncates, clears, the file). Finally, you then write your altered data there.

Rough example illustrating the process. No actual modification of the data is done here, and no assumptions as to the layout of the data are made.

Code:

set fid [open "myfile" "RDONLY"]set data [read $fid]close $fid#manipulate $dataset fid [open "myfile" "WRONLY CREAT TRUNC"]puts $fid $dataclose $fid

Statistics: Posted by nml375 — Sat Feb 14, 2009 8:51 pm

Writing, reading and deleting data from a file

2009-02-14T19:00:47-04:00

Hi,

I'm making a script that requires writing, reading and deleting entries from a file. With the help of http://wiki.tcl.tk/367, I was able to make the bot write to a file and read it. However, I don't know how to delete a certain entry.

I'm using this to write to the file:

Code:

 set data [lrange $text 1 end] set fileId [open Triggers/triggers.$chan "w"] puts -nonewline $fileId $data close $fileId

How can I make the bot remove a line from the file?

Thanks in advance,
Fill

Statistics: Posted by Fill — Sat Feb 14, 2009 7:00 pm