Final answer:
To append a file called 'file1' to a tar archive, use the command 'tar -rvf archive_name.tar file1' in a Unix-like terminal. Ensure the tar archive is not compressed, as appending to compressed archives is not possible without decompression.
Step-by-step explanation:
To append a file, known as "file1", to a tar archive, you can use the tar command with the '-rvf' option in a Unix-like operating system. The 'r' stands for 'append' and 'vf' stands for 'verbose' and 'file' respectively. Here is a step-by-step explanation of how to do this:
Open the terminal on your Unix system.
Use the command tar -rvf archive_name.tar file1, replacing 'archive_name.tar' with the actual name of your tar archive and 'file1' with the name of the file you wish to add.
Press Enter to execute the command.
If the operation is successful, tar will list the file it appended to the archive.
Note that you cannot append files to a compressed tar archive (i.e., .tar.gz or .tar.bz2). It needs to be decompressed first.