### 4.2 Starting your Program

`run`
`r`
  Use the `run` command to start your program under gdb. You must first specify the program name (except on VxWorks) with an argument to gdb (see Getting In and Out of gdb), or by using the `file` or `exec-file` command (see Commands to Specify Files).

If you are running your program in an execution environment that supports processes, `run` creates an inferior process and makes that process run your program. (In environments without processes, `run` jumps to the start of your program.)

The execution of a program is affected by certain information it receives from its superior. gdb provides ways to specify this information, which you must do before starting your program. (You can change it after starting your program, but such changes only affect your program the next time you start it.) This information may be divided into four categories:

The arguments.
  Specify the arguments to give your program as the arguments of the `run` command. If a shell is available on your target, the shell is used to pass the arguments, so that you may use normal conventions (such as wildcard expansion or variable substitution) in describing the arguments. In Unix systems, you can control which shell is used with the `SHELL` environment variable. See Your Program's Arguments.
The environment.
  Your program normally inherits its environment from gdb, but you can use the gdb commands `set environment` and `unset environment` to change parts of the environment that affect your program. See Your Program's Environment.
The working directory.
  Your program inherits its working directory from gdb. You can set the gdb working directory with the `cd` command in gdb. See Your Program's Working Directory.
The standard input and output.
  Your program normally uses the same device for standard input and standard output as gdb is using. You can redirect input and output in the `run` command line, or you can use the `tty` command to set a different device for your program. See Your Program's Input and Output.

  Warning: While input and output redirection work, you cannot use pipes to pass the output of the program you are debugging to another program; if you attempt this, gdb is likely to wind up debugging the wrong program.

When you issue the `run` command, your program begins to execute immediately. See Stopping and Continuing, for discussion of how to arrange for your program to stop. Once your program has stopped, you may call functions in your program, using the `print` or `call` commands. See Examining Data.

If the modification time of your symbol file has changed since the last time gdb read its symbols, gdb discards its symbol table, and reads it again. When it does this, gdb tries to retain your current breakpoints.

`start`
  The name of the main procedure can vary from language to language. With C or C`++`, the main procedure name is always `main`, but other languages such as Ada do not require a specific name for their main procedure. The debugger provides a convenient way to start the execution of the program and to stop at the beginning of the main procedure, depending on the language used.

  The ``start`' command does the equivalent of setting a temporary breakpoint at the beginning of the main procedure and then invoking the ``run`' command.

  Some programs contain an elaboration phase where some startup code is executed before the main procedure is called. This depends on the languages used to write your program. In C`++`, for instance, constructors for static and global objects are executed before `main` is called. It is therefore possible that the debugger stops before reaching the main procedure. However, the temporary breakpoint will remain to halt execution.

  Specify the arguments to give to your program as arguments to the ``start`' command. These arguments will be given verbatim to the underlying ``run`' command. Note that the same arguments will be reused if no argument is provided during subsequent calls to ``start`' or ``run`'.

  It is sometimes necessary to debug the program during elaboration. In these cases, using the `start` command would stop the execution of your program too late, as the program would have already completed the elaboration phase. Under these circumstances, insert breakpoints in your elaboration code before running your program.

`set exec-wrapper` wrapper
`show exec-wrapper`
`unset exec-wrapper`
  When ``exec-wrapper`' is set, the specified wrapper is used to launch programs for debugging. gdb starts your program with a shell command of the form `exec` wrapper program. Quoting is added to program and its arguments, but not to wrapper, so you should add quotes if appropriate for your shell. The wrapper runs until it executes your program, and then gdb takes control.

  You can use any program that eventually calls `execve` with its arguments as a wrapper. Several standard Unix utilities do this, e.g. `env` and `nohup`. Any Unix shell script ending with `exec "$@"` will also work.

  For example, you can use `env` to pass an environment variable to the debugged program, without setting the variable in your shell's environment:

                (gdb) set exec-wrapper env 'LD_PRELOAD=libtest.so'
                (gdb) run

  This command is available when debugging locally on most targets, excluding djgpp, Cygwin, MS Windows, and QNX Neutrino.