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.
- Add directory to the front of the
PATHenvironment variable (the search path for executables) that will be passed to your program. The value of
PATHused 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
pathcommand. gdb replaces . in the directory argument (with the current path) before adding directory to the search path.
- Display the list of search paths for executables (the
- 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
set environmentvarname [
- 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
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.)
- Remove variable varname from the environment to be passed to your
program. This is different from set env varname =;
unset environmentremoves the variable from the environment, rather than assigning it an empty value.
Warning: On Unix systems, gdb runs your program using
the shell indicated
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