For 2023 (and 2024 ...) - we are now fully retired from IT training. We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.
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Tcl - apparently odd behaviour of string trimleft
Question:
Why does this code:
set dir "D:/JNN/proc/"
set tempname "D:/JNN/proc/Doc-99887767.dat"
set cname [string trimleft $tempname $dir]
puts $cname
report
-99887767.dat
but this code:
set dir "D:/JNN/proc/"
set tempname "D:/JNN/proc/Foc-99887767.dat"
set cname [string trimleft $tempname $dir]
puts $cname
report
Foc-99887767.dat
Answer
The second parameter to string trimleft (the one that's in $dir in the example) is treated as a list of individual characters to be removed. And in the first example, the "D" "o" and "c" are stripped off the beginning of the file name because they also occur in the directory name.
Suggestion
If you want to strip the leading directory information off a path and file name, you may find it better to use regsub
set cname [regsub {.*/} $tempname ""]
the apparently spurious .* meaning we trim to the last / rather than the first. (written 2012-01-13, updated 2012-01-14)
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles T205 - Tcl/Tk - String Handling in Tcl [404] How to check that a string contains a number in Tcl - (2005-08-06) [779] The fragility of pancakes - and better structures - (2006-06-26) [943] Matching within multiline strings, and ignoring case in regular expressions - (2006-11-25) [1403] Square Bracket protection in Tcl - (2007-10-23) [1410] Tcl / regsub - changing a string and using interesting bits - (2007-10-27) [1601] Replacing the last comma with an and - (2008-04-04) [2472] split and join in tcl and expect - (2009-10-23) [3192] Tcl - Some example of HOW TO in handling data files and formats - (2011-03-04) [3285] Extracting data from a string / line from file - Tcl - (2011-05-10) [4205] Regular Expression Substitution - Tcl - (2013-11-12) [4454] Everything is a string - even a list - (2015-03-11) [4455] Working out distance between places, using OS grid references and a program in Tcl - (2015-03-11)
Some other Articles
Melksham Area - buses, trains, cycles, and roads. Meeting, 17.1.2012Transport in Cambridgeshire - seen by an outside observer. What can Wiltshire learn?A busy start to 2012How to do multidimensional arrays (or rather lists and hashes) in PerlTcl - apparently odd behaviour of string trimleftMultiple buttons calling the same proc in wish (tcl/tk)Perl functions such as chop change their input parametersNew in Java 7 - and why we are not running public Java 7 coursesAdding Expect on top of Tcl - what is it and where can I get a training course to learn about it?Comparing loop commands in Tcl
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