To execute a script by its name alone, without prepending its path (e.g., ./script.sh), the directory containing the script must be listed in the PATH environment variable. The PATH variable is a colon-separated list of directories that the shell searches for executables. The command export PATH=$PATH:/home/user/scripts appends the new directory /home/user/scripts to the existing list of directories in the PATH. This makes any executable file within that directory runnable from any location in the filesystem by simply typing its name. The export command makes this variable available to subsequently executed commands.

A. The SHELL variable defines the user's login shell (e.g., /bin/bash), not the search path for executables. This command has incorrect syntax and purpose.

B. The TERM variable specifies the terminal type being used (e.g., xterm, vt100). It has no effect on how the shell finds and executes commands.

D. This command uses incorrect syntax. alias is a separate shell builtin for creating command shortcuts, and export is used for environment variables.

1. The GNU Project. (2022). Bash Reference Manual

Section 6.7 Bash Variables. The manual defines the PATH variable as "The search path for commands. It is a colon-separated list of directories in which the shell looks for commands."

2. Massachusetts Institute of Technology (MIT) OpenCourseWare. (2020). 6.003

The Shell. Lecture notes describe the PATH variable and its role in command execution

explaining how to modify it to include new directories.

3. The Linux Documentation Project. (2004). Bash Guide for Beginners

Chapter 3. The Bash environment. Section 3.2.2 discusses shell initialization files and the importance of setting the PATH variable correctly.