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Commands

The command for any rule is just a Tcl script. The command must be on the line immediately after a rule, and must be indented by at least one space or tab. The command ends at the first blank line or line that has a character at the start of the line.

Unlike GNU make, which by default evaluates each line in a command separately in its own process, tclmake evaluates the command as a whole. So a variable that is defined on one line, for example, can be referenced in a later line.

Also unlike GNU make, which requires that tabs be used to indent the lines in a command, tclmake accepts any whitespace for indenting.

If a line starts with the character @, then the Tcl command starting on that line will not be echoed to the console. (Note that @ can be used only as the first character of a line that starts a new Tcl command that is not within another Tcl command.)

The command will have any make-variables substituted into it. The command will also have the following automatic variables substituted:

$@

  • The name of the target that is being updated. In the tclIndex example, this variable will be tclIndex.

$!

  • The name of the target that is being updated that caused this target to be updated. This is like going "up the call stack," and is used only in very special circumstances (see Recursive tclmakes). This variable is unique to tclmake.

$<

  • The name of the first dependency. In the tclIndex example, this variable will be the first file in TCL_SRCS.

$?

  • The names of the dependencies that have been updated before the target. In the tclIndex example, this variable will be the files in TCL_SRCS that are newer than tclIndex.

$^ $+

  • The names of all dependencies. In the tclIndex example, this variable will be the value of TCL_SRCS.

$*

  • The stem of a pattern-match rule -- that is, the part of the file name that matched the % symbol.

All commands are executed in the global namespace of a special interpreter created at the beginning of the goal evaluation process, which is separate from the interpreter executing the tclmake program code. All global variables created by the execution of a command in the special interpreter are deleted when the command is finished, to prevent collision of variable values between commands. If a user wishes to persist state from execution of one command to another, it can be done by other means that avoid use of global variables, such as creating special namespace variables. However, doing so goes against the typical assumption of statelessness of individual make commands, and should be done with caution.

The working directory is also reset each time a command completes, to the value it had when the command was first called. Thus any directory changes done within the command are reverted.