### 4.4 Your Program's Environment

The environment consists of a set of environment variables and their values. Environment variables conventionally record such things as your user name, your home directory, your terminal type, and your search path for programs to run. Usually you set up environment variables with the shell and they are inherited by all the other programs you run. When debugging, it can be useful to try running your program with a modified environment without having to start gdb over again.

`path` directory
  Add directory to the front of the `PATH` environment variable (the search path for executables) that will be passed to your program. The value of `PATH` used by gdb does not change. You may specify several directory names, separated by whitespace or by a system-dependent separator character (‘`:`’ on Unix, ‘`;`’ on MS-DOS and MS-Windows). If directory is already in the path, it is moved to the front, so it is searched sooner.

  You can use the string ‘`$cwd`’ to refer to whatever is the current working directory at the time gdb searches the path. If you use ‘`.`’ instead, it refers to the directory where you executed the `path` command. gdb replaces ‘`.`’ in the directory argument (with the current path) before adding directory to the search path.

`show paths`
  Display the list of search paths for executables (the `PATH` environment variable).

`show environment` [varname]
  Print the value of environment variable varname to be given to your program when it starts. If you do not supply varname, print the names and values of all environment variables to be given to your program. You can abbreviate `environment` as `env`.

`set environment` varname [`=`value]
  Set environment variable varname to value. The value changes for your program only, not for gdb itself. value may be any string; the values of environment variables are just strings, and any interpretation is supplied by your program itself. The value parameter is optional; if it is eliminated, the variable is set to a null value.

  For example, this command:

                set env USER = foo

  tells the debugged program, when subsequently run, that its user is named ‘`foo`’. (The spaces around ‘`=`’ are used for clarity here; they are not actually required.)

`unset environment` varname
  Remove variable varname from the environment to be passed to your program. This is different from ‘`set env varname =`’; `unset environment` removes the variable from the environment, rather than assigning it an empty value.

Warning: On Unix systems, gdb runs your program using the shell indicated by your `SHELL` environment variable if it exists (or `/bin/sh` if not). If your `SHELL` variable names a shell that runs an initialization file—such as `.cshrc` for C-shell, or `.bashrc` for BASH—any variables you set in that file affect your program. You may wish to move setting of environment variables to files that are only run when you sign on, such as `.login` or `.profile`.