What is a Tcl error?

What is a Tcl error?

Many Tcl commands generate an error condition when there is a problem (command invoked with invalid arguments, runtime error, etc). This error condition, or error for short, interrupts the running program and causes Tcl to print an error message before terminating.

What are the basic TCL commands?

Examples of TCL commands:

  • COMMIT– commits a Transaction.
  • ROLLBACK– rollbacks a transaction in case of any error occurs.
  • SAVEPOINT–sets a savepoint within a transaction.
  • SET TRANSACTION–specify characteristics for the transaction.

What is catch command in Tcl?

DESCRIPTION. The catch command may be used to prevent errors from aborting command interpretation. Catch calls the Tcl interpreter recursively to execute script, and always returns a TCL_OK code, regardless of any errors that might occur while executing script.

What do you mean by Tcl list out TCL commands?

Tcl command is actually a list of words, with the first word representing the command to be executed. The next words represent the arguments. In order to group the words into a single argument, we enclose multiple words with “” or {}.

What is eval Tcl?

Eval concatenates all its arguments in the same fashion as the concat command, passes the concatenated string to the Tcl interpreter recursively, and returns the result of that evaluation (or any error generated by it).

What is a Tcl code?

Tcl (pronounced “tickle” or as an initialism) is a high-level, general-purpose, interpreted, dynamic programming language. It was designed with the goal of being very simple but powerful. Tcl interpreters are available for many operating systems, allowing Tcl code to run on a wide variety of systems.

What does Tcl mean?

Telephone Communication Limited
TCL Technology (originally an abbreviation for Telephone Communication Limited) is a Chinese multinational electronics company headquartered in Huizhou, Guangdong Province.

What is the catch command in Tcl-error handling?

In the above catch command syntax, script is the code to be executed, resultVarName is variable that holds the error or the result. The catch command returns 0 if there is no error, and 1 if there is an error.

What is the return code of TCL _ error?

Errors during evaluation of a script are indicated by a return code of TCL_ERROR. The other exceptional return codes are returned by the return, break, and continuecommands and in other special situations as documented.

What is the try command in Tcl 8.6?

Tcl 8.6 added a new command for handling errors though. The try command is rather more like what you’re used to with Python: It also supports finally and trap clauses for guaranteed actions and more sophisticated error handling respectively. For example (something which it is annoying to write with catch ):

When does a proc return a value in Tcl?

In Tcl, a proc may return a value, but it always returns a status. When a Tcl command or procedure encounters an error during its execution, the global variable errorInfois set, and an error condition is generated. If you have proc athat called proc bthat called cthat called d, if dgenerates an error, the “call stack” will unwind.