*** An [exec] ''Gotcha'' ***

Tcl looks for the command to be [exec]'ed in a sequence of directories part of which may be described by the [PATH].  This sequence is documented in the exec man page: http://www.tcl.tk/man/tcl/TclCmd/exec.htm and differs among operating systems.

A potential '''gotcha''' occurs when the PATH used by the user's shell differs from that of Tcl.  This is a '''gotcha''' for all programs that need to execute other programs and isn't restricted to interpreters such as Perl/Python/PHP let alone Tcl.

When this happens calling the command from the shell or commandline (say Dos) works but ''execing'' it from Tcl either fails completely or calls a different program with the same name.
This is not an uncommon problem.

E.g. With [ImageMagick] installed on Windows

======
# this works
dos> convert a.tiff a.jpg

#but this results in an error
tclsh> exec convert a.tiff a.jpg
  Invalid Parameter - a.jpg
  Child process exited abnormally 
======

What's happening here is that Tcl is invoking C:\WINDOWS\system32\convert.exe while dos invokes
the convert.exe installed in the ImageMagick directory.

The moral of the story is not to assume that if a command works from the commandline, then it will also be ''execed'' successfully by Tcl or any other interpreter or program.

----
!!!!!!
%| [Category Command] |%
!!!!!!