Question

I have a file contain lines with path to the files. Sometimes a path contain SHELL environment variable and I want to check the file existence.
The following is my solution:

set fh [open "the_file_contain_path" "r"]

while {![eof $fh]} { 
  set line [gets $fh]
  if {[regexp -- {\$\S+} $line]} {
    catch {exec /usr/local/bin/tcsh -c "echo  $line" } line
      if {![file exists $line]} {
        puts "ERROR: the file $line is not exists"
      }
  }
}

I sure there is more elegant solution without using

/usr/local/bin/tcsh –c

Answer 1

You can capture the variable name in the regexp command and do a lookup in Tcl’s global env array. Also, your use of eof as the while condition means your loop will interate one time too many (see http://phaseit.net/claird/comp.lang.tcl/fmm.html#eof)

set fh [open "the_file_contain_path" "r"]

while {[gets $fh line] != -1} { 
  # this can handle "$FOO/bar/$BAZ"
  if {[string first {$} $line] != -1} {
    regsub -all {(\$)(\w+)} $line {\1::env(\2)} new
    set line [subst -nocommand -nobackslashes $new]
  }

  if {![file exists $line]} {
    puts "ERROR: the file $line does not exist"
  }
}