pam_getenv

This is a C library function, not a shell command.

#include <security/pam_appl.h>
const char *pam_getenv(pam_handle_t *pamh, const char *name);

pamh
    A pointer to the PAM handle, which represents the current PAM transaction or session context. This handle is typically obtained via pam_start().

name
    The name of the environment variable (a C string) to retrieve. For example, "DISPLAY" or "HOME".

The pam_getenv is a function from the PAM (Pluggable Authentication Modules) library, not a standalone shell command. It is used by PAM service modules or PAM-aware applications to retrieve environment variables that have been set within the current PAM handle or session context. These variables are typically populated by other PAM modules (e.g., using pam_putenv or pam_setenv) and can include crucial information like DISPLAY, XAUTHORITY, or custom variables needed for session setup or application execution. This function is vital for ensuring that the correct environment is established and inherited by the user's session or by subsequent modules within the PAM stack, allowing for seamless integration of various system services during authentication and session management.

pam_getenv is a library function, not an executable command. It must be called programmatically from a C application or a PAM module. The returned string points to data within the PAM handle and should not be modified or freed by the caller. The string is only valid for the lifetime of the PAM transaction or until another PAM function call modifies the environment.

The pam_getenv function returns a constant pointer to the string value of the environment variable if found. If the variable is not found within the PAM handle's environment, it returns NULL.

This function is primarily used by PAM modules (e.g., session modules like pam_systemd or custom modules) or by applications that interact directly with PAM to retrieve environment variables that are set by other modules during the authentication, account, password, or session management phases. It allows modules to pass crucial context (like DISPLAY, XAUTHORITY, etc.) to the application or subsequent modules in the PAM stack.

pam_getenv is an integral part of the PAM (Pluggable Authentication Modules) framework, which was developed to provide a flexible and extensible way to authenticate users and manage sessions. Its inclusion reflects the need for modules to communicate and share environmental context, ensuring that a consistent and secure environment is set up for a user's session. It has been a standard part of the PAM library since its early adoption and specification.

pam(7), pam_appl(3), pam_putenv(3), pam_setenv(3), pam_getenvlist(3), pam_start(3), pam_end(3), pam_env(8), pam_exec(8)