+# Test a file for a hashbang to identify executable scripts on Windows.
+proc is_shellscript {filename} {
+ if {![file exists $filename]} {return 0}
+ set f [open $filename r]
+ fconfigure $f -encoding binary
+ set magic [read $f 2]
+ close $f
+ return [expr {$magic eq "#!"}]
+}
+
+# Run a command connected via pipes on stdout.
+# This is for use with textconv filters and uses sh -c "..." to allow it to
+# contain a command with arguments. On windows we must check for shell
+# scripts specifically otherwise just call the filter command.
+proc open_cmd_pipe {cmd path} {
+ global env
+ if {![file executable [shellpath]]} {
+ set exe [auto_execok [lindex $cmd 0]]
+ if {[is_shellscript [lindex $exe 0]]} {
+ set run [linsert [auto_execok sh] end -c "$cmd \"\$0\"" $path]
+ } else {
+ set run [concat $exe [lrange $cmd 1 end] $path]
+ }
+ } else {
+ set run [list [shellpath] -c "$cmd \"\$0\"" $path]
+ }
+ return [open |$run r]
+}
+