RHCSA Essential Command-Line Tools Flashcards

What does the redirection operator '>>' do?

Answer: Appends stdout to a file without overwriting

>> appends standard output to the end of a file, preserving existing content.

Which command lists all environment variables currently set in the shell?

Answer: env

env without arguments prints all environment variables and their values to stdout.

When using 'find', what does '-mtime -2' mean?

Answer: Files modified within the last 2 days

In find, -mtime -2 selects files whose modification time is less than 2*24 hours ago (within the last 2 days).

What does 'chmod 755 script.sh' set on the file?

Answer: Owner: rwx, Group: r-x, Others: r-x

Octal 7=rwx, 5=r-x, so 755 gives the owner full permissions and group/others read+execute.

Which command creates a hard link named 'link1' pointing to 'file1'?

Answer: ln file1 link1

ln without -s creates a hard link; both names refer to the same inode on the same filesystem.

What is the effect of 'echo $?' after a command returns successfully?

Answer: Prints 0

$? holds the exit status of the most recently executed command; 0 indicates success.

Which command would archive and compress the directory '/data' into a gzip-compressed tarball named 'data.tar.gz'?

Answer: tar -czf data.tar.gz /data

tar -czf uses -c to create, -z for gzip compression, and -f to name the output file.