I am trying to parse a CSV to check if one of the headers is present.
Sometimes I'd expect a fifth colomn with arbitraryHead
date time value result arbitraryHead
val1 d1 10 fail
val2 d2 15 norun
I was trying to read the first line then print it. But that is not working...
How can I read the first line and print all the headers?
set fh [open $csv_file r]
set data [list]
set line [gets $fh line]
lappend data [split $line ,]
close $fh
foreach x $data {
puts "$x\n"
}
When reading a CSV file, it's best to use the csv package in Tcllib, as that handles all the awkward edge cases in that format.
In particular, csv::split is especially useful (along with csv::join when creating a CSV file). Or the various functions that act as wrappers around it. Here's how you'd use it in your case
package require csv
set fh [open $csv_file r]
# Your data appears to be actually tab-separated, not comma-separated...
set data [csv::split [gets $fh] "\t"]
close $fh
foreach x $data {
puts "$x\n"
}
Your actual immediate bug was this:
set line [gets $fh line]
The two-argument form of gets writes the line it reads into the variable named in the second argument, and returns the length of line read (or -1 on failure to read a complete line, which can be useful in complex cases that aren't important here). You're then assigning that value to the same variable with set, losing the string that was written there. You should instead use one of the following (except that you should use a properly-tested package for reading CSV files):
gets $fh line
set line [gets $fh]
The one-argument form of gets returns the line it read, which can make it harder to distinguish errors but is highly convenient.
The simplest you can do is string match operation, just look for the desired header you wanted to check.
As requested in the following code I am checking "arbitraryHead"
set fh [open $csv_file r]
set contents [read $fh ]
foreach x $contents {
if {[string match "*arbitraryHead*" $x]} {
puts "HEAD FOUND"
}
}
close $fh
Hope this address your issue
Related
I have a VHDL file which has a line like this:
constant version_nr :integer := 47;
I want to increment the number in this line in the file. Is there a way to accomplish this with TCL?
This is principally a string operation. The tricky bit is finding the line to operate on and picking the number out of it. This can be occasionally awkward, but it is mainly a matter of choosing a suitable regular expression (as this is the kind of parsing task that they excel at). A raw RE to do the matching would be this:
^\s*constant\s+version_nr\s*:integer\s*:=\s*\d+\s*;\s*$
This is essentially converting all possible places for a whitespace sequence into \s* (except where whitespace is mandatory, which becomes \s+) and matching the number with \d+, i.e., a digit sequence. We then add in parentheses to capture the interesting substrings, which are the prefix, the number, and the suffix:
^(\s*constant\s+version_nr\s*:integer\s*:=\s*)(\d+)(\s*;\s*)$
Now we have enough to make the line transform (which we'll do as a procedure so we can give it a nice name):
proc lineTransform {line} {
set RE {^(\s*constant\s+version_nr\s*:integer\s*:=\s*)(\d+)(\s*;\s*)$}
if {[regexp $RE $line -> prefix number suffix]} {
# If we match, we increment the number...
incr number
# And reconcatenate it with the prefix and suffix to make the new line
set line $prefix$number$suffix
}
return $line
}
In Tcl 8.7 (which you won't be using yet) you can write this as this more succinct form:
proc lineTransform {line} {
# Yes, this version can be a single (long) line if you want
set RE {^(\s*constant\s+version_nr\s*:integer\s*:=\s*)(\d+)(\s*;\s*)$}
regsub -command $RE $line {apply {{- prefix number suffix} {
# Apply the increment when the RE matches and build the resulting line
string cat $prefix [incr number] $suffix
}}}
}
Now that we have a line transform, we've just got to apply that to all the lines of the file. This is easily done with a file that fits in memory (up to a few hundred MB) but requires additional measures for larger files as you need to stream from one file to another:
proc transformSmallFile {filename} {
# Read data into memory first
set f [open $filename]
set data [read $f]
close $f
# Then write it back out, applying the transform as we go
set f [open $filename w]
foreach line [split $data "\n"] {
puts $f [transformLine $line]
}
close $f
}
proc transformLargeFile {filename} {
set fin [open $filename]
# The [file tempfile] command makes working with temporary files easier
set fout [file tempfile tmp [file normalize $filename]]
# A streaming transform; requires that input and output files be different
while {[gets $fin line] >= 0} {
puts $fout [transformLine $line]
}
# Close both channels; flushes everything to disk too
close $fin
close $fout
# Rename our temporary over the original input file, replacing it
file rename $tmp $filename
}
I want to print character from the next line:
say :
when this variable dum=183 exists in file , then print the very next charater from next line.
Note : I am using tcl
Thanks,
This should help you get started.
The typical idioms for working with a file one line at a time are:
1) linewise reading:
set f [open thefile.txt]
while {[gets $f line] >= 0} {
# work with the line of text in "line"
}
close $f
2) block reading with line splitting:
set f [open thefile.txt]
set text [read $f]
close $f
set lines [split [string trim $text] \n]
foreach line $lines {
# work with the line of text in "line"
}
This can be simplified by using a package:
package require fileutil
::fileutil::foreachLine line thefile.txt {
# work with the line of text in "line"
}
Another way is to search and extract using a regular expression. This is the worst method as it is inflexible and very likely to be buggy in use.
set f [open thefile.txt]
set text [read $f]
close $f
# this regular expression is an example
if {[regexp {\ydum\y[^\n]*.(.)} $text -> thecharacter]} {
# the character you wanted should be in "thecharacter"
}
Documentation:
>= (operator),
close,
fileutil (package),
foreach,
gets,
if,
open,
package,
read,
regexp,
set,
split,
string,
while,
Syntax of Tcl regular expressions
How do I read more than a single line in a file using tcl? That is by default the gets command reads till a new line is found, how do I change this behaviour to read a file till a specific character is found?
If you don't mind reading over a bit, you can do it by looping with gets or read in a loop:
set data ""
while {[gets $chan line] >= 0} {
set idx [string first $whatToLookFor $line]
if {$idx == -1} {
append data $line\n
} else {
# Decrement idx; don't want first character of $whatToLookFor
append data [string range $line 0 [incr idx -1]]
break
}
}
# Data has everything up to but not including $whatToLookFor
If you're looking for multiline patterns, I suggest reading the whole file into memory and working on that. It's just so much easier than trying to write a correct matcher:
set data [read $chan]
set idx [string first $whatToLookFor $data]
if {$idx > -1} {
set data [string range $data 0 [incr idx -1]]
}
This latter form will also work just fine with binary data. Just remember to fconfigure $chan -translation binary first if you're doing that.
Use fconfigure.
set fp [open "somefile" r]
fconfigure $fp -eofchar "char"
set data [read $fp]
close $fp
In addition to Donal's good advice, you could get a list of records by reading the whole file and splitting on the record separator:
package require textutil::split
set records [textutil::splitx [read $chan] "record_separator"]
Documentation
The following code is skipping odd lines like 1,3,5,7,9......wat has to be done to get all lines from a file using this code
set in [filename r]
seek $in 0 start
while { [gets $in line] != -1 } {
gets $in line
puts $line
}
You're doing gets $in line once in the condition and once inside the loop body; the line read in the condition gets lost as a result. You probably want to remove the one in the loop body.
You have used gets twice that is why you are getting only the odd lines
Other solution:
Instead of using gets I prefer using read function to read the whole contents of the file and then process those line by line. So we are in complete control of operation on file by having it as list of lines
set fileName [lindex $argv 0]
catch {set fptr [open $fileName r]} ;
set contents [read $fptr] ;#Read the file contents
close $fptr ;Close the file since it has been read now
set splitCont [split $contents "\n"] ;#Split the files contents on new line
splitCont is the list which has has lines of the file as individual elements
I have a file in here which has multiple set statements. However I want to extract the lines of my interest. Can the following code help
set in [open filename r]
seek $in 0 start
while{ [gets $in line ] != -1} {
regexp (line to be extracted)
}
Other solution:
Instead of using gets I prefer using read function to read the whole contents of the file and then process those line by line. So we are in complete control of operation on file by having it as list of lines
set fileName [lindex $argv 0]
catch {set fptr [open $fileName r]} ;
set contents [read -nonewline $fptr] ;#Read the file contents
close $fptr ;#Close the file since it has been read now
set splitCont [split $contents "\n"] ;#Split the files contents on new line
foreach ele $splitCont {
if {[regexp {^set +(\S+) +(.*)} $ele -> name value]} {
puts "The name \"$name\" maps to the value \"$value\""
}
}
How to run this code:
say above code is saved in test.tcl
Then
tclsh test.tcl FileName
FileName is full path of file unless the file is in the same directory where the program is.
First, you don't need to seek to the beginning straight after opening a file for reading; that's where it starts.
Second, the pattern for reading a file is this:
set f [open $filename]
while {[gets $f line] > -1} {
# Process lines
if {[regexp {^set +(\S+) +(.*)} $line -> name value]} {
puts "The name \"$name\" maps to the value \"$value\""
}
}
close $f
OK, that's a very simple RE in the middle there (and for more complicated files you'll need several) but that's the general pattern. Note that, as usual for Tcl, the space after the while command word is important, as is the space between the while expression and the while body. For specific help with what RE to use for particular types of input data, ask further questions here on Stack Overflow.
Yet another solution:
as it looks like the source is a TCL script, create a new safe interpreter using interp which only has the set command exposed (and any others you need), hide all other commands and replace unknown to just skip anything unrecognised. source the input in this interpreter
Here is yet another solution: use the file scanning feature of Tclx. Please look up Tclx for more info. I like this solution for that you can have several scanmatch blocks.
package require Tclx
# Open a file, skip error checking for simplicity
set inputFile [open sample.tcl r]
# Scan the file
set scanHandle [scancontext create]
scanmatch $scanHandle {^\s*set} {
lassign $matchInfo(line) setCmd varName varValue; # parse the line
puts "$varName = $varValue"
}
scanfile $scanHandle $inputFile
close $inputFile
Yet another solution: use the grep command from the fileutil package:
package require fileutil
puts [lindex $argv 0]
set matchedLines [fileutil::grep {^\s*set} [lindex $argv 0]]
foreach line $matchedLines {
# Each line is in format: filename:line, for example
# sample.tcl:set foo bar
set varName [lindex $line 1]
set varValue [lindex $line 2]
puts "$varName = $varValue"
}
I've read your comments so far, and if I understand you correctly your input data file has 6 (or 9, depending which comment) data fields per line, separated by spaces. You want to use a regexp to parse them into 6 (or 9) arrays or lists, one per data field.
If so, I'd try something like this (using lists):
set f [open $filename]
while {[gets $f line] > -1} {
# Process lines
if {[regexp {(\S+) (\S+) (\S+) (\S+) (\S+) (\S+)} $line -> name source drain gate bulk inst]} {
lappend nameL $name
lappend sourceL $source
lappend drainL $drain
lappend gateL $gate
lappend bulkL $bulk
lappend instL $inst
}
}
close $f
Now you should have a set of 6 lists, one per field, with one entry in the list for each item in your input file. To access the i-th name, for example, you grab $nameL[$i].
If (as I suspect) your main goal is to get the parameters of the device whose name is "foo", you'd use a structure like this:
set name "foo"
set i [lsearch $nameL $name]
if {$i != -1} {
set source $sourceL[$i]
} else {
puts "item $name not found."
set source ''
# or set to 0, or whatever "not found" marker you like
}
set File [ open $fileName r ]
while { [ gets $File line ] >= 0 } {
regex {(set) ([a-zA-Z0-0]+) (.*)} $line str1 str2 str3 str4
#str2 contains "set";
#str3 contains variable to be set;
#str4 contains the value to be set;
close $File
}