JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD MCA 2018 LINUX PROGRAMMING Previous Question Paper (January - 2018 - R15)

Special parameters in the shell are internal variables that provide information about the script or command execution. Key special parameters include:

• $0: Expands to the name of the shell or shell script.
• $n: Expands to the nth positional parameter (where n is a digit).
• $#: Expands to the number of positional parameters.
• $*: Expands to all positional parameters starting from one.
• $@: Expands to all positional parameters, treating each as a separate word.
• $?: Expands to the exit status of the most recently executed foreground pipeline.
• $$: Expands to the process ID of the shell.
• $!: Expands to the process ID of the most recently executed background command.

A hard link is a directory entry that associates a filename with an existing inode on the file system. It essentially creates an additional name for the same data on the disk.

Advantages: Hard links are efficient as they do not consume extra disk space for data, and the file remains accessible as long as at least one hard link exists, even if the original filename is deleted.

Disadvantages: They cannot span across different file systems or partitions, and they cannot be created for directories to prevent circular references in the file system structure.