Q: Unix file permissions (chmod): Which command grants execute permission to user, group, and others for every file named 'letter' in the current directory?

Introduction / Context: Unix permissions control who can read, write, and execute files. The chmod command changes these modes for the user (u), group (g), and others (o). Granting execute permission is commonly required for scripts and binaries before they can be run. Given Data / Assumptions: Target filename is literally 'letter' (potentially multiple files named 'letter' across directories, but here we act in the current directory). We want execute permission for all classes: user, group, and others. We assume standard POSIX chmod syntax. Concept / Approach: The symbolic chmod form uses u, g, o to denote permission classes and +x to add execute permission. Combining them as ugo+x applies the change to all three classes simultaneously for the specified file(s). Step-by-Step Solution: Identify permission classes: user (u), group (g), others (o).Determine operation: add execute permission = +x.Combine in one command: chmod ugo+x letterConfirm with ls -l to verify the x bits are set where intended. Verification / Alternative check: Run ls -l letter before and after the chmod. You should see mode bits change, for example, from -rw-r--r-- to -rwxr-xr-x if no other changes occurred. This validates that execute permission is now available to all classes. Why Other Options Are Wrong: chmod ugo+r letter: Adds read permission, not execute. chmod ugo+rw letter: Adds read and write, but not execute. chmod u+x letter: Grants execute only to the owner (user), not group and others. None of the above: Incorrect because chmod ugo+x letter achieves the stated goal. Common Pitfalls: Forgetting that directories require execute (search) permission to enter; applying +x to data files that are not scripts/binaries is harmless but unnecessary. Also, ensure scripts have a proper shebang (for example, #!/bin/sh) when executed. Final Answer: chmod ugo+x letter

Q: Copying and renaming a file between directories (Unix cp): Which command copies the file 'wb' from the 'programs' directory to the 'misc' directory, naming the destination file 'wbx'?

Introduction / Context: File management on Unix commonly involves copying files between directories and optionally renaming them in the process. The cp utility provides a simple syntax to specify a source path and a destination path that may include a new filename. Given Data / Assumptions: Source file: programs/wb (relative path). Destination directory: misc/ with a new filename wbx. Standard POSIX cp behavior is assumed. Concept / Approach: The cp command takes the form cp source destination. If destination refers to a directory, cp copies into that directory with the same filename; if destination includes a trailing filename, the file is copied and simultaneously renamed. This is ideal for duplicating and renaming in one step. Step-by-Step Solution: Choose the correct utility: cp (copy in Unix).Specify relative source path: programs/wb.Specify destination path and new name: misc/wbx.Final command: cp programs/wb misc/wbx Verification / Alternative check: After running the command, ls -l misc/wbx should list the new file. The original programs/wb remains unchanged. Optionally, compare checksums with sum or md5sum to confirm identity. Why Other Options Are Wrong: copy programs/wb misc/wbx: 'copy' is a DOS command, not standard on Unix. tar programs/wb misc/wbx: tar creates/extracts archives; it does not copy single files in this manner. copy a:programs/wb b:misc/wbx: DOS drive-letter syntax; not applicable to Unix paths. None of the above: Incorrect because cp programs/wb misc/wbx is correct. Common Pitfalls: Forgetting quotes when paths contain spaces; overwriting existing files unintentionally (use cp -i for interactive prompts). For recursive directory copies, use cp -r, but for single files the basic cp is sufficient. Final Answer: cp programs/wb misc/wbx

Q: UNIX/Linux file permissions (octal to symbolic): The command 'chmod 761 note' sets permissions using octal notation. Which equivalent symbolic-mode command applies the same permissions to the file named 'note'?

Introduction / Context: Understanding UNIX/Linux permissions is essential for system administration and secure software development. Permissions can be set either with octal numbers (like 761) or with symbolic expressions (like u=rwx,g=rw,o=x). This question checks whether you can translate octal permission codes into their exact symbolic equivalents for user (u), group (g), and others (o). Given Data / Assumptions: Target file: note. Octal permissions specified: 761. Standard UNIX permission mapping is used. Concept / Approach: Octal permission digits map to read (4), write (2), and execute (1) bits. Sum the bit values per class. Left to right the octal digits represent user, group, and others. Translate each digit to the corresponding r, w, x letters in symbolic notation. Step-by-Step Solution: Split 761 into user=7, group=6, others=1.For user=7: 4+2+1 = rwx, so u=rwx.For group=6: 4+2 = rw-, so g=rw.For others=1: 1 = --x, so o=x.Combine: chmod u=rwx,g=rw,o=x note Verification / Alternative check: Run ls -l note after applying permissions. You should see rwxrw--x (or equivalent, depending on default umask and file type) aligning with 761. Why Other Options Are Wrong: a: chmod 167 note reorders classes (would set u=1,g=6,o=7), not the intended 761 mapping. c: Misspelled command and invalid syntax. d: There is no syntax like 4=7 in chmod; classes are u, g, o (or a). e: Not applicable because the correct symbolic form is available. Common Pitfalls: Confusing the order of classes (u,g,o), forgetting that 6 means rw (no x), or mixing up symbolic add mode (u+x) with full assignment mode (u=...). Final Answer: chmod u=rwx,g=rw,o=x note

Q: UNIX account database fields: In /etc/passwd (the classic UNIX user account file), what does the 7th field represent?

Introduction / Context: The /etc/passwd file contains core details for user accounts on UNIX-like systems. Each record is colon-separated and historically included the hashed password (now typically shadowed). Administrators and developers should know what each field means to troubleshoot logins, shells, and user environments. Given Data / Assumptions: We are referring to the standard 7-field /etc/passwd format. Fields are colon-separated: name:passwd:uid:gid:gecos:home:shell. Modern systems often store the actual password hash in /etc/shadow. Concept / Approach: Count fields from left to right and map them to their roles. The 7th field is the user's login shell—such as /bin/bash, /bin/sh, /usr/sbin/nologin—defining the program invoked at login or when spawning an interactive session. Step-by-Step Solution: Field 1: login name (username).Field 2: password placeholder (often x or *), real hash in /etc/shadow.Field 3: user ID (UID).Field 4: group ID (GID).Field 5: GECOS/comment (full name or info).Field 6: home directory path.Field 7: login shell program. Verification / Alternative check: Use getent passwd username to view the entry. The last colon-separated field will show the shell path (for example, /bin/bash). Why Other Options Are Wrong: a: The password hash is not the 7th field and is usually in /etc/shadow. b: The login (username) is the 1st field. d: Home directory is the 6th field, not the 7th. e: Not applicable because the 7th field is the shell. Common Pitfalls: Confusing home and shell positions; assuming the password is still stored in /etc/passwd rather than shadowed; overlooking accounts that use a non-interactive shell for service users. Final Answer: shell

Q: vi text editor (Vim/vi classic): Which vi command replaces the single character under the cursor and then enters insert mode so you can type any number of replacement characters?

Introduction / Context: Efficient editing in vi/Vim relies on powerful single-keystroke commands. Knowing the difference between change, substitute, append, and insert is key to rapid text manipulation. Here, we focus on replacing exactly one character and then continuing to type new text seamlessly. Given Data / Assumptions: We are using classic vi keybindings. Cursor is on the character to be replaced. We want to replace that character and continue inserting any number of characters. Concept / Approach: The command s (substitute) deletes the character under the cursor and puts you into insert mode. You can then type any amount of text. By contrast, r replaces only one character and remains in normal mode; S substitutes the entire line; a appends after the cursor; i inserts before the cursor. Step-by-Step Solution: Position the cursor over the character to change.Press s. The character is deleted and the editor enters insert mode.Type the new text (any length).Press Esc to return to normal mode when done.Optionally use csw (in Vim) and other text objects for advanced cases. Verification / Alternative check: Compare s vs r: rx changes one character to x and stops; s deletes the character and keeps you inserting, which matches the requirement. Why Other Options Are Wrong: b: S substitutes the whole line, not a single character. c: a appends after the cursor; it does not remove the original character. d: i inserts before the cursor; the original character remains unless you delete it manually. e: Not applicable because s is correct. Common Pitfalls: Using r instead of s when multiple characters are needed; forgetting to press Esc to leave insert mode; confusing S with s, which affects a vastly different scope. Final Answer: s

Q: df (disk free) usage: Which option with the df command includes a grand total of disk space across the listed file systems?

Introduction / Context: The df command summarizes disk capacity and usage across mounted file systems. Some UNIX variants provide an option to display a grand total line that sums the sizes and usage for easier capacity planning. Knowing per-platform flags helps administrators standardize reports and scripts. Given Data / Assumptions: We are using a traditional UNIX variant where df supports a total line option. Question asks for the option that includes the total amount of disk space across file systems. We are not focusing on filesystem-type filters or inode-only reports. Concept / Approach: Historically, some df implementations use a specific flag to add a final total line. On certain UNIX variants, the -t flag provides a total summary line (note that on GNU/Linux, -c is used, and -t filters by type). In exam-style questions tied to classical UNIX, -t is commonly taught as the totalizing flag. Step-by-Step Solution: Run df with the specified option to list mounted file systems.Observe an additional “total” line providing aggregate blocks, used, and available figures.Use human-readable switches (where available) for clarity.Compare with without the option to confirm presence of the total line.Document behavior differences across UNIX flavors in team runbooks. Verification / Alternative check: On GNU coreutils, df -c provides totals, whereas -t filters by type. On exam contexts referencing traditional UNIX, -t is used for totals. Always check man df on your platform to verify exact semantics. Why Other Options Are Wrong: b: Not a standard df option. c: -4 is not a standard df flag for totals. d: -i reports inode statistics, not total space lines. e: Not applicable under the assumed traditional semantics. Common Pitfalls: Assuming GNU/Linux semantics on all platforms; confusing total lines with file-system type filters; forgetting that scripting across heterogeneous systems requires conditional flags. Final Answer: -t

Q: Granting execute permission (owner only): Which chmod command gives the file owner execute permission on the file 'note' (without changing other existing permissions)?

Introduction / Context: Selective permission changes are common when turning a script into an executable. The chmod command supports symbolic modes that add (+), remove (-), or set (=) permissions for user (u), group (g), and others (o) without affecting unrelated bits. Given Data / Assumptions: Target file: note. Goal: add execute permission for the owner only. Other existing permissions should remain unchanged. Concept / Approach: Use symbolic mode with the user class: u+x means “add execute for user.” It leaves group and others untouched. Verification is done via ls -l, which shows permission triplets as rwx. Step-by-Step Solution: Run chmod u+x note.Confirm with ls -l note that the owner's execute bit is set.If the file is a script, ensure it has a valid shebang (for example, #!/bin/sh).Optionally adjust group or others with g+x or o+x if needed.Use chmod u-x to remove execute permission later. Verification / Alternative check: Execute the file (./note) if it is a script or binary. If permission denied appears, re-check owner and execute bit, and ensure the filesystem is mounted with exec allowed. Why Other Options Are Wrong: a: Grants execute to group, not owner. b: Adds write, not execute, to owner. d: Grants execute to user, group, and others, broader than requested. e: Not applicable; option c is correct. Common Pitfalls: Accidentally overexposing a file with ugo+x; forgetting executable shebang for scripts; modifying permissions on a non-executable mount. Final Answer: chmod u+x note

Q: Copying a file between directories on UNIX: Which command correctly copies the file 'programs/wb' into the directory 'misc' keeping the same name?

Introduction / Context: On UNIX/Linux systems, file copy operations use the cp command. To copy a single file into a target directory preserving its filename, you specify the source path followed by the destination directory. Mastering cp syntax is essential for reliable file management and scripting. Given Data / Assumptions: Source: programs/wb. Destination directory: misc. We want to retain the filename wb. Concept / Approach: When the destination is a directory, cp places the source file inside it with the same name. If you wanted to rename the file, you would specify the new filename after the destination directory path. The command differs from DOS/Windows copy syntax and from archiving tools like tar. Step-by-Step Solution: Ensure the misc directory exists (mkdir -p misc if needed).Run cp programs/wb miscVerify success with ls -l misc/wbUse cp -i to prompt before overwrite, or cp -p to preserve timestamps/ownership if desired.For recursive directory copy, use cp -r (not required here). Verification / Alternative check: Compare checksums (for example, sha256sum programs/wb misc/wb) to confirm a perfect copy. If permissions differ, add cp -p. Why Other Options Are Wrong: a: copy is a DOS command, not UNIX cp. c: tar is for archiving; not a simple copy. d: DOS-style drive letters are not used on UNIX. e: Not applicable, option b is correct. Common Pitfalls: Forgetting that an existing misc/wb may be overwritten; using relative paths from the wrong working directory; confusing cp with mv (move/rename). Final Answer: cp programs/wb misc

Question 1

Safely removing year-old files with confirmation (Unix find): Which command removes files (with a user confirmation prompt for each) that have neither been accessed nor modified in the last 365 days under /usr/?

Accepted Answer

Introduction / Context: Cleaning up stale files on Unix must be done carefully. The find command can select files by access and modification times, while -ok executes a command with an interactive confirmation before each deletion, reducing the risk of accidental data loss. Given Data / Assumptions: Target directory tree: /usr/* (all first-level entries under /usr). Staleness criteria: not accessed for >= 365 days and not modified for >= 365 days. Safety requirement: prompt before deleting each file. We want a single pipeline-free command using find's built-in primitives. Concept / Approach: find supports primary tests for modification time (mtime) and access time (atime), both expressed in days. Parentheses group conditions; -a denotes logical AND. The -ok action runs the specified command prompting '<< ... >> ?' for each candidate. The {} placeholder expands to the found pathname, and commands end with '\;'. Step-by-Step Solution: Select the search roots: /usr/.Build the predicate: $ -mtime +365 -a -atime +365 $.Use a safe action: -ok rm {} \; to prompt before removal.Combine into a single command: find /usr/ $ -mtime +365 -a -atime +365 $ -ok rm {} \; Verification / Alternative check: First replace -ok with -print to audit matches: find /usr/* $ -mtime +365 -a -atime +365 $ -print. After verifying, switch to -ok rm {} \; for prompted deletions, or use -exec rm {} \; if non-interactive removal is acceptable. Why Other Options Are Wrong: find -mtime +365 | rm: Pipes a list of names into rm incorrectly; also lacks atime criteria and prompts. grep (/usr/) -mtime +365 | -ok rm: Mixes grep with find semantics; invalid syntax. find -name -mtime +365 / -ok rm: Malformed ordering and missing arguments. None of the above: Incorrect because a correct, safe find command exists (option A). Common Pitfalls: Forgetting to escape parentheses in shells; omitting {} and \; in -ok/-exec; using only mtime when access time policy also matters; and running as root without first auditing with -print, which can be hazardous. Final Answer: find /usr/ $ -mtime +365 -a -atime +365 $ -ok rm {} \;

Question 2

Viewing the end of a file on Unix/Linux: Which command displays the tail (last lines) of a text file on the terminal by default?

Accepted Answer

Introduction / Context: When troubleshooting logs or monitoring activity, it is often necessary to see the most recent lines appended to a file. Unix provides a dedicated utility for this purpose, enabling both static viewing and live following. Given Data / Assumptions: We want the command that shows the end of a file. Default behavior should display the last 10 lines unless otherwise specified. We are using standard Unix command-line tools. Concept / Approach: The tail utility prints the final portion of files. Common flags include -n for a specific number of lines and -f to follow file growth in real time (useful for log monitoring). Other listed options either do something else or are not valid commands. Step-by-Step Solution: Identify the canonical tool: 'tail'.Recall default behavior: displays last 10 lines.Optional usage: tail -n 50 file.txt or tail -f /var/log/syslog to follow updates.Conclude that 'tail' is the required command. Verification / Alternative check: Running tail /etc/passwd on a Unix system prints the last 10 entries. Adding -f keeps the file open and prints new additions as they occur, confirming its role for end-of-file viewing. Why Other Options Are Wrong: head -r: head shows the beginning of a file; '-r' is not portable and still would not show the tail. eof, bof: Not standard Unix commands; EOF/BOF are concepts, not executables. None of the above: Incorrect because 'tail' is correct. Common Pitfalls: Confusing 'head' and 'tail'; expecting -f to terminate automatically; forgetting to use sudo or appropriate permissions when tailing protected logs. Final Answer: tail

Question 3

Identify your terminal device on Unix/Linux: Which command prints the device file name (for example, /dev/tty2 or /dev/pts/0) of the terminal session you are currently using?

Accepted Answer

Introduction / Context: Interactive sessions in Unix are attached to pseudo-terminals or console devices. Knowing exactly which device your shell is connected to can help with redirection, permission debugging, and multi-user administration. Given Data / Assumptions: The user is logged in via a terminal or pseudo-terminal (SSH, console, or TTY). We want the command that directly prints the device path of the current terminal. We are using standard core utilities. Concept / Approach: The tty program writes the file name of the terminal connected to standard input. If the shell is attached to a TTY-like device, it returns a path under /dev; otherwise, it may print 'not a tty' when input is not a terminal. Step-by-Step Solution: Run the command: ttyObserve typical output: /dev/pts/0 on modern systems or /dev/tty1 on consoles.Use cases: feed device names to scripts or adjust permissions appropriately.Therefore, 'tty' is the correct command. Verification / Alternative check: Piping or redirecting input can change behavior; for example, running tty < /dev/null will report not a tty. In an interactive shell, plain tty always prints the device name, confirming its identity purpose. Why Other Options Are Wrong: who: Lists users logged in and their terminals, but it does not identify your current controlling terminal directly without parsing. ls: Lists directory contents; unrelated to terminal identity. stty: Configures terminal line settings; does not by itself print the device file path. None of the above: Incorrect because 'tty' is precisely the identity tool. Common Pitfalls: Confusing 'who am i' with 'tty'; the former prints your login name and terminal line but is less direct than tty's device path output. Also, note that scripts running non-interactively may not have a controlling TTY. Final Answer: tty

Question 4

Unix file permissions (chmod): Which command grants execute permission to user, group, and others for every file named 'letter' in the current directory?

Accepted Answer

Introduction / Context: Unix permissions control who can read, write, and execute files. The chmod command changes these modes for the user (u), group (g), and others (o). Granting execute permission is commonly required for scripts and binaries before they can be run. Given Data / Assumptions: Target filename is literally 'letter' (potentially multiple files named 'letter' across directories, but here we act in the current directory). We want execute permission for all classes: user, group, and others. We assume standard POSIX chmod syntax. Concept / Approach: The symbolic chmod form uses u, g, o to denote permission classes and +x to add execute permission. Combining them as ugo+x applies the change to all three classes simultaneously for the specified file(s). Step-by-Step Solution: Identify permission classes: user (u), group (g), others (o).Determine operation: add execute permission = +x.Combine in one command: chmod ugo+x letterConfirm with ls -l to verify the x bits are set where intended. Verification / Alternative check: Run ls -l letter before and after the chmod. You should see mode bits change, for example, from -rw-r--r-- to -rwxr-xr-x if no other changes occurred. This validates that execute permission is now available to all classes. Why Other Options Are Wrong: chmod ugo+r letter: Adds read permission, not execute. chmod ugo+rw letter: Adds read and write, but not execute. chmod u+x letter: Grants execute only to the owner (user), not group and others. None of the above: Incorrect because chmod ugo+x letter achieves the stated goal. Common Pitfalls: Forgetting that directories require execute (search) permission to enter; applying +x to data files that are not scripts/binaries is harmless but unnecessary. Also, ensure scripts have a proper shebang (for example, #!/bin/sh) when executed. Final Answer: chmod ugo+x letter

Question 5

Copying and renaming a file between directories (Unix cp): Which command copies the file 'wb' from the 'programs' directory to the 'misc' directory, naming the destination file 'wbx'?

Accepted Answer

Introduction / Context: File management on Unix commonly involves copying files between directories and optionally renaming them in the process. The cp utility provides a simple syntax to specify a source path and a destination path that may include a new filename. Given Data / Assumptions: Source file: programs/wb (relative path). Destination directory: misc/ with a new filename wbx. Standard POSIX cp behavior is assumed. Concept / Approach: The cp command takes the form cp source destination. If destination refers to a directory, cp copies into that directory with the same filename; if destination includes a trailing filename, the file is copied and simultaneously renamed. This is ideal for duplicating and renaming in one step. Step-by-Step Solution: Choose the correct utility: cp (copy in Unix).Specify relative source path: programs/wb.Specify destination path and new name: misc/wbx.Final command: cp programs/wb misc/wbx Verification / Alternative check: After running the command, ls -l misc/wbx should list the new file. The original programs/wb remains unchanged. Optionally, compare checksums with sum or md5sum to confirm identity. Why Other Options Are Wrong: copy programs/wb misc/wbx: 'copy' is a DOS command, not standard on Unix. tar programs/wb misc/wbx: tar creates/extracts archives; it does not copy single files in this manner. copy a:programs/wb b:misc/wbx: DOS drive-letter syntax; not applicable to Unix paths. None of the above: Incorrect because cp programs/wb misc/wbx is correct. Common Pitfalls: Forgetting quotes when paths contain spaces; overwriting existing files unintentionally (use cp -i for interactive prompts). For recursive directory copies, use cp -r, but for single files the basic cp is sufficient. Final Answer: cp programs/wb misc/wbx

Question 6

UNIX/Linux file permissions (octal to symbolic): The command 'chmod 761 note' sets permissions using octal notation. Which equivalent symbolic-mode command applies the same permissions to the file named 'note'?

Accepted Answer

Introduction / Context: Understanding UNIX/Linux permissions is essential for system administration and secure software development. Permissions can be set either with octal numbers (like 761) or with symbolic expressions (like u=rwx,g=rw,o=x). This question checks whether you can translate octal permission codes into their exact symbolic equivalents for user (u), group (g), and others (o). Given Data / Assumptions: Target file: note. Octal permissions specified: 761. Standard UNIX permission mapping is used. Concept / Approach: Octal permission digits map to read (4), write (2), and execute (1) bits. Sum the bit values per class. Left to right the octal digits represent user, group, and others. Translate each digit to the corresponding r, w, x letters in symbolic notation. Step-by-Step Solution: Split 761 into user=7, group=6, others=1.For user=7: 4+2+1 = rwx, so u=rwx.For group=6: 4+2 = rw-, so g=rw.For others=1: 1 = --x, so o=x.Combine: chmod u=rwx,g=rw,o=x note Verification / Alternative check: Run ls -l note after applying permissions. You should see rwxrw--x (or equivalent, depending on default umask and file type) aligning with 761. Why Other Options Are Wrong: a: chmod 167 note reorders classes (would set u=1,g=6,o=7), not the intended 761 mapping. c: Misspelled command and invalid syntax. d: There is no syntax like 4=7 in chmod; classes are u, g, o (or a). e: Not applicable because the correct symbolic form is available. Common Pitfalls: Confusing the order of classes (u,g,o), forgetting that 6 means rw (no x), or mixing up symbolic add mode (u+x) with full assignment mode (u=...). Final Answer: chmod u=rwx,g=rw,o=x note

Question 7

UNIX account database fields: In /etc/passwd (the classic UNIX user account file), what does the 7th field represent?

Accepted Answer

Introduction / Context: The /etc/passwd file contains core details for user accounts on UNIX-like systems. Each record is colon-separated and historically included the hashed password (now typically shadowed). Administrators and developers should know what each field means to troubleshoot logins, shells, and user environments. Given Data / Assumptions: We are referring to the standard 7-field /etc/passwd format. Fields are colon-separated: name:passwd:uid:gid:gecos:home:shell. Modern systems often store the actual password hash in /etc/shadow. Concept / Approach: Count fields from left to right and map them to their roles. The 7th field is the user's login shell—such as /bin/bash, /bin/sh, /usr/sbin/nologin—defining the program invoked at login or when spawning an interactive session. Step-by-Step Solution: Field 1: login name (username).Field 2: password placeholder (often x or *), real hash in /etc/shadow.Field 3: user ID (UID).Field 4: group ID (GID).Field 5: GECOS/comment (full name or info).Field 6: home directory path.Field 7: login shell program. Verification / Alternative check: Use getent passwd username to view the entry. The last colon-separated field will show the shell path (for example, /bin/bash). Why Other Options Are Wrong: a: The password hash is not the 7th field and is usually in /etc/shadow. b: The login (username) is the 1st field. d: Home directory is the 6th field, not the 7th. e: Not applicable because the 7th field is the shell. Common Pitfalls: Confusing home and shell positions; assuming the password is still stored in /etc/passwd rather than shadowed; overlooking accounts that use a non-interactive shell for service users. Final Answer: shell

Question 8

vi text editor (Vim/vi classic): Which vi command replaces the single character under the cursor and then enters insert mode so you can type any number of replacement characters?

Accepted Answer

Introduction / Context: Efficient editing in vi/Vim relies on powerful single-keystroke commands. Knowing the difference between change, substitute, append, and insert is key to rapid text manipulation. Here, we focus on replacing exactly one character and then continuing to type new text seamlessly. Given Data / Assumptions: We are using classic vi keybindings. Cursor is on the character to be replaced. We want to replace that character and continue inserting any number of characters. Concept / Approach: The command s (substitute) deletes the character under the cursor and puts you into insert mode. You can then type any amount of text. By contrast, r replaces only one character and remains in normal mode; S substitutes the entire line; a appends after the cursor; i inserts before the cursor. Step-by-Step Solution: Position the cursor over the character to change.Press s. The character is deleted and the editor enters insert mode.Type the new text (any length).Press Esc to return to normal mode when done.Optionally use csw (in Vim) and other text objects for advanced cases. Verification / Alternative check: Compare s vs r: rx changes one character to x and stops; s deletes the character and keeps you inserting, which matches the requirement. Why Other Options Are Wrong: b: S substitutes the whole line, not a single character. c: a appends after the cursor; it does not remove the original character. d: i inserts before the cursor; the original character remains unless you delete it manually. e: Not applicable because s is correct. Common Pitfalls: Using r instead of s when multiple characters are needed; forgetting to press Esc to leave insert mode; confusing S with s, which affects a vastly different scope. Final Answer: s

Question 9

df (disk free) usage: Which option with the df command includes a grand total of disk space across the listed file systems?

Accepted Answer

Introduction / Context: The df command summarizes disk capacity and usage across mounted file systems. Some UNIX variants provide an option to display a grand total line that sums the sizes and usage for easier capacity planning. Knowing per-platform flags helps administrators standardize reports and scripts. Given Data / Assumptions: We are using a traditional UNIX variant where df supports a total line option. Question asks for the option that includes the total amount of disk space across file systems. We are not focusing on filesystem-type filters or inode-only reports. Concept / Approach: Historically, some df implementations use a specific flag to add a final total line. On certain UNIX variants, the -t flag provides a total summary line (note that on GNU/Linux, -c is used, and -t filters by type). In exam-style questions tied to classical UNIX, -t is commonly taught as the totalizing flag. Step-by-Step Solution: Run df with the specified option to list mounted file systems.Observe an additional “total” line providing aggregate blocks, used, and available figures.Use human-readable switches (where available) for clarity.Compare with without the option to confirm presence of the total line.Document behavior differences across UNIX flavors in team runbooks. Verification / Alternative check: On GNU coreutils, df -c provides totals, whereas -t filters by type. On exam contexts referencing traditional UNIX, -t is used for totals. Always check man df on your platform to verify exact semantics. Why Other Options Are Wrong: b: Not a standard df option. c: -4 is not a standard df flag for totals. d: -i reports inode statistics, not total space lines. e: Not applicable under the assumed traditional semantics. Common Pitfalls: Assuming GNU/Linux semantics on all platforms; confusing total lines with file-system type filters; forgetting that scripting across heterogeneous systems requires conditional flags. Final Answer: -t

Question 10

Granting execute permission (owner only): Which chmod command gives the file owner execute permission on the file 'note' (without changing other existing permissions)?

Accepted Answer

Introduction / Context: Selective permission changes are common when turning a script into an executable. The chmod command supports symbolic modes that add (+), remove (-), or set (=) permissions for user (u), group (g), and others (o) without affecting unrelated bits. Given Data / Assumptions: Target file: note. Goal: add execute permission for the owner only. Other existing permissions should remain unchanged. Concept / Approach: Use symbolic mode with the user class: u+x means “add execute for user.” It leaves group and others untouched. Verification is done via ls -l, which shows permission triplets as rwx. Step-by-Step Solution: Run chmod u+x note.Confirm with ls -l note that the owner's execute bit is set.If the file is a script, ensure it has a valid shebang (for example, #!/bin/sh).Optionally adjust group or others with g+x or o+x if needed.Use chmod u-x to remove execute permission later. Verification / Alternative check: Execute the file (./note) if it is a script or binary. If permission denied appears, re-check owner and execute bit, and ensure the filesystem is mounted with exec allowed. Why Other Options Are Wrong: a: Grants execute to group, not owner. b: Adds write, not execute, to owner. d: Grants execute to user, group, and others, broader than requested. e: Not applicable; option c is correct. Common Pitfalls: Accidentally overexposing a file with ugo+x; forgetting executable shebang for scripts; modifying permissions on a non-executable mount. Final Answer: chmod u+x note

Question 11

Copying a file between directories on UNIX: Which command correctly copies the file 'programs/wb' into the directory 'misc' keeping the same name?

Accepted Answer

Introduction / Context: On UNIX/Linux systems, file copy operations use the cp command. To copy a single file into a target directory preserving its filename, you specify the source path followed by the destination directory. Mastering cp syntax is essential for reliable file management and scripting. Given Data / Assumptions: Source: programs/wb. Destination directory: misc. We want to retain the filename wb. Concept / Approach: When the destination is a directory, cp places the source file inside it with the same name. If you wanted to rename the file, you would specify the new filename after the destination directory path. The command differs from DOS/Windows copy syntax and from archiving tools like tar. Step-by-Step Solution: Ensure the misc directory exists (mkdir -p misc if needed).Run cp programs/wb miscVerify success with ls -l misc/wbUse cp -i to prompt before overwrite, or cp -p to preserve timestamps/ownership if desired.For recursive directory copy, use cp -r (not required here). Verification / Alternative check: Compare checksums (for example, sha256sum programs/wb misc/wb) to confirm a perfect copy. If permissions differ, add cp -p. Why Other Options Are Wrong: a: copy is a DOS command, not UNIX cp. c: tar is for archiving; not a simple copy. d: DOS-style drive letters are not used on UNIX. e: Not applicable, option b is correct. Common Pitfalls: Forgetting that an existing misc/wb may be overwritten; using relative paths from the wrong working directory; confusing cp with mv (move/rename). Final Answer: cp programs/wb misc

Question 12

Finding user startup files across the system: Which find command locates all files named '.profile' anywhere on the system and prints their full paths?

Accepted Answer

Introduction / Context: User shell initialization files such as .profile influence environment variables, PATH, and login behavior. Administrators often need to audit or update all .profile files on a system. The find utility provides a recursive, flexible way to search the entire filesystem or a subtree by filename. Given Data / Assumptions: Target filename: .profile (note the leading dot). We want to search system-wide from root (/) and print full paths. We have adequate permissions to traverse directories (or use sudo where appropriate). Concept / Approach: The command find / -name '.profile' -print recursively descends from the root directory, matching files whose basename equals .profile and printing their paths. Quoting the name prevents shell globbing and correctly preserves the leading dot. -print is explicit for clarity on classic UNIX find implementations. Step-by-Step Solution: Open a terminal with sufficient privileges.Run: find / -name '.profile' -printReview the list of paths to user home directories (for example, /home/alex/.profile).Optionally restrict scope: find /home -name '.profile' -printUse -type f to limit to regular files if needed. Verification / Alternative check: Manually navigate to a reported path and run ls -la to confirm the file exists and is a regular file. For a smaller search, use find ~ -name '.profile' -print to search only the current user's home. Why Other Options Are Wrong: b: ls profile looks in the current directory and for profile (without dot), not recursively. c: cd /.profile attempts to change into a file; also wrong path. d: l -u .profile is not a standard command. e: Searches only the current user's home, not the entire system as required. Common Pitfalls: Forgetting the leading dot; failing to quote the pattern; running from a restricted account that cannot traverse certain directories. Final Answer: find / -name '.profile' -print

Question 13

Setting permissions for all user classes: Which UNIX command sets permissions on a file by specifying bits for user, group, and others in one operation?

Accepted Answer

Introduction / Context: File security in UNIX is enforced through ownership (user and group) and permissions (read, write, execute) for user, group, and others. Correctly choosing the tool for permission changes prevents configuration drift and security lapses. Given Data / Assumptions: We need to set or modify permissions for all three classes (u,g,o). We are not changing group ownership or user ownership. Standard POSIX-style utilities are available. Concept / Approach: The chmod command sets permission bits using octal or symbolic modes. chown changes file owner (and optionally group). chgrp changes the group association. There is no standard command named chusr. Step-by-Step Solution: Use chmod u=rwx,g=rx,o=r file to set an explicit policy.Alternatively use octal, for example chmod 754 file.Verify with ls -l.Use recursive option -R when applying to directories and their contents.Document the policy for repeatability. Verification / Alternative check: Run stat file to view detailed mode bits and confirm chmod changes applied as expected. Why Other Options Are Wrong: a: chgrp changes the group owner, not permission bits. b: chown changes user/group ownership, not the permissions. d: chusr is not a standard UNIX command. e: Not applicable because chmod is correct. Common Pitfalls: Using chmod = (assignment) when intending to add or remove bits; forgetting execute bits on directories; omitting -R for nested trees. Final Answer: chmod

Question 14

Recursive deletion: Which rm command removes all files in the current directory as well as every file and subdirectory within its subdirectories?

Accepted Answer

Introduction / Context: Recursive deletion is a powerful but dangerous operation on UNIX systems. The rm utility can remove directories and their contents when used with the appropriate options. Proper understanding prevents accidental data loss and ensures safe automation in scripts. Given Data / Assumptions: We want to delete files in the current directory and everything nested beneath it (subdirectories and files). We are not specifically handling hidden files; patterns can be adjusted. We have the necessary permissions and understand the risk. Concept / Approach: rm -r enables recursive removal of directories. When combined with a wildcard like , it targets all non-hidden entries in the current directory, descending into directories to remove their contents as well. Add -i to prompt before each removal or -f to force without prompts based on safety needs. Step-by-Step Solution: Confirm you are in the correct directory (pwd).List contents (ls -A) before proceeding.Run rm -r * to remove all non-hidden entries recursively.Consider rm -r . carefully if hidden entries must be removed; beware of . and .. exclusions.Verify with ls afterward to ensure intended removal. Verification / Alternative check: Test on a disposable directory structure created with mkdir -p and touch to confirm behavior. Use tree or find to verify no remnants remain. Why Other Options Are Wrong: a: rm * removes only files (and empty directories in some shells with special options) in the current directory, not recursive subdirectories. c: rm all is not a standard command. d: rm . is DOS-style and misses names without dots; still not recursive. e: Not applicable because rm -r * is correct. Common Pitfalls: Running from the wrong directory; forgetting hidden files; omitting quotes when using dangerous patterns in scripts; not using -i for interactive confirmation in sensitive locations. Final Answer: rm -r *

Question 15

Counting lines, words, and characters: Which UNIX command reports the number of lines, words, and bytes/characters in a file?

Accepted Answer

Introduction / Context: Quickly summarizing the size of text files is a common need for developers, data engineers, and sysadmins. UNIX provides a compact utility for this: wc (word count). It can be combined with options and pipelines to provide precise metrics in scripts and investigations. Given Data / Assumptions: We need counts for lines, words, and characters/bytes. We are using standard POSIX-style utilities. File encoding and locale may affect the character interpretation, but wc remains the standard tool. Concept / Approach: wc reports counts; options like -l, -w, -c (or -m) select lines, words, and bytes/characters respectively. Without options, wc prints all three counts followed by the filename. It is often used in shell pipelines to measure the output of other commands. Step-by-Step Solution: Run wc filename to see lines, words, bytes and the filename.Use wc -l filename for just lines; wc -w for words; wc -c for bytes; wc -m for characters on some systems.Pipe output from other commands: cat file | wc -lCombine with find and xargs to summarize multiple files.Redirect output to logs for auditing. Verification / Alternative check: Spot-check by manually counting a small file’s lines and words to confirm wc behavior. Use hexdump or od to explore byte counts for encodings. Why Other Options Are Wrong: a, c, d: Not standard UNIX utilities. e: Not applicable because wc is correct. Common Pitfalls: Confusing bytes (-c) with characters (-m) in multibyte locales; forgetting to quote file patterns; relying on wc behavior across different UNIX variants without checking man pages. Final Answer: wc

Question 16

UNIX/Linux command basics  Which command should you use to create a new directory (folder) from the shell?

Accepted Answer

Introduction / Context: Creating directories is one of the first file-system skills in UNIX/Linux administration. The shell offers a dedicated utility to make new folders at any path, with optional creation of parent directories and permission control. Knowing the correct command, flags, and typical usage prevents errors and improves scripting reliability. Given Data / Assumptions: Operating in a UNIX/Linux command-line environment (bash, zsh, sh). Destination path either exists or you have permission to create it. No special characters in directory names beyond what the shell can handle with proper quoting. Concept / Approach: The standard tool is mkdir (make directory). It creates one or more directories supplied as arguments. Important flags include -p to create missing parent directories, and -m mode to set permissions at creation. The command is portable across distributions and POSIX-compliant shells. Step-by-Step Solution: To create a single directory in the current path: mkdir reports.To create nested parents: mkdir -p projects/2025/q1.To set permissions immediately: mkdir -m 750 teamshare.Verify using ls -ld directory_name to confirm ownership and mode. Verification / Alternative check: Run ls after creation to see the new entry. If -p is used and the directory exists, mkdir -p does nothing and returns success, which is useful in idempotent scripts. Why Other Options Are Wrong: crdir (Option A) and cr (Option D) are not standard UNIX commands.md (Option B) is a DOS/Windows alias, not portable on UNIX/Linux systems.None of the above (Option E) is wrong because mkdir is correct. Common Pitfalls: Forgetting quotes when names contain spaces. Omitting -p when parents do not exist. Creating directories in protected paths without sudo, causing Permission denied. Final Answer: mkdir

Question 17

vi editor navigation (current line search)  In the classic vi editor, which motion finds and moves the cursor forward to the first occurrence of a specified character ch on the current line?

Accepted Answer

Introduction / Context: Efficient navigation in the vi editor relies on single-keystroke motions. When you need to jump directly to a specific character ahead on the same line, vi provides concise commands that reduce cursor keystrokes and speed up edits in code and configuration files. Given Data / Assumptions: You are using vi (or Vim in compatible mode) in normal mode. You want to move forward on the current line to the first occurrence of a character, denoted here as ch. Character search is case-sensitive in vi motions. Concept / Approach: The motion f{char} moves the cursor forward to the next occurrence of {char} on the current line. The mnemonic is “find”. The related t{char} motion moves to the position just before {char} (“till”). You can repeat the last f/t search using ; to go forward again or , to go backward to the previous match. Step-by-Step Solution: Enter normal mode (press Esc if necessary).Type f followed by the target character, e.g., f( or f, or fa.The cursor jumps to the first matching character to the right on the same line.Use ; to move to the next occurrence or , to move to the previous one. Verification / Alternative check: Compare with tch (“till”): t, places the cursor before the comma rather than on it. If no match exists to the right, vi reports a beep/error and the cursor does not move. Why Other Options Are Wrong: tch (Option A) stops just before the character, not on it.rch (Option C) and ech (Option D) are not valid vi motions.None of the above (Option E) is incorrect because fch is the intended notation for f followed by ch. Common Pitfalls: Typing f then two characters; vi accepts only a single target character. Forgetting to stay on the same line; these motions do not cross line breaks. Confusing search motions (/) which scan multiple lines with f/t which are single-line motions. Final Answer: fch

Question 18

Archiving vs. copying directory trees on UNIX/Linux  Which command is traditionally used to copy directory structures “in and out” of archives and is well suited for whole-tree backups and restores?

Accepted Answer

Introduction / Context: UNIX/Linux offers several tools for copying files and entire directory trees. While cp copies files and directories on the filesystem, cpio excels at moving directory structures into and out of archive streams, making it ideal for backups, restores, and piping with find and other tools. Given Data / Assumptions: You need to preserve directory structures and optionally metadata. Streaming to devices or files (tapes, files, or pipes) is acceptable. Familiarity with pipelines and redirection. Concept / Approach: cpio reads file lists from standard input and creates or extracts archives. Typical usage pairs find with cpio to archive an entire tree reliably. It supports various formats and can preserve ownership, modes, and timestamps when run with appropriate privileges and flags. Step-by-Step Solution: Create an archive: find /src -depth -print | cpio -ov > backup.cpioExtract an archive: cpio -idv < backup.cpioCopy across filesystems via pipe: (cd /src; find . -print) | (cd /dst; cpio -pdmv)Verify with ls -lR or checksums to ensure integrity post-restore. Verification / Alternative check: Compare with tar for similar functionality. While tar is more prevalent today, cpio remains standard on many UNIX systems and integrates cleanly with find-generated file lists. Why Other Options Are Wrong: cp (Option A) copies files/dirs directly but is not an archive in/out utility.cp -p (Option C) preserves mode/timestamps/ownership but still is cp, not an archiver.copy (Option D) is a DOS/Windows command, not UNIX. Common Pitfalls: Forgetting to supply file lists to cpio via stdin. Not using -pdm when “pass-through” copying a tree between directories. Neglecting ownership preservation without proper privileges. Final Answer: cpio

Question 19

chmod operators (symbolic mode)  Which operator with chmod assigns absolute permissions by setting them exactly (replacing previous bits) for the specified classes?

Accepted Answer

Introduction / Context: File permissions in UNIX/Linux can be modified using chmod in symbolic or numeric modes. Symbolic mode uses operators to add, remove, or set permissions for user (u), group (g), others (o), or all (a). Understanding these operators is vital for secure configuration and reproducible scripts. Given Data / Assumptions: Symbolic notation: classes u, g, o, a and permissions r, w, x. Operators available: +, -, =. Goal: assign an exact set of permissions, replacing previous ones. Concept / Approach: The operator = sets the permissions absolutely, meaning only the listed bits remain for the targeted classes. In contrast, + adds bits and - removes bits relative to the current state. Numeric mode (e.g., 750) is also “absolute,” but in symbolic syntax, = is the exact-set operator. Step-by-Step Solution: To set group to read-only exactly: chmod g=r fileTo set user read/write, group read, others none: chmod u=rw,g=r,o= fileCompare with additive: chmod g+r leaves any existing x intact.Verify permissions: ls -l file Verification / Alternative check: Use stat or ls -l before and after to confirm that = replaced previous bits instead of toggling incrementally. Why Other Options Are Wrong: + (Option A) adds bits without clearing others.- (Option B) removes bits without affecting the rest.% (Option D) is not a chmod operator. Common Pitfalls: Using + when you intend to reset the class entirely. Omitting a class (defaults to a, which may be broader than intended). Forgetting commas between multiple specifications. Final Answer: =

Question 20

vi editor insertion at end of line  In vi, which single-key command appends text at the end of the current line and enters insert mode there?

Accepted Answer

Introduction / Context: vi provides several ways to start inserting text relative to the cursor position. Mastering these entry points accelerates editing source code and configuration files by reducing keystrokes and unnecessary cursor movement. Given Data / Assumptions: You are in normal mode (Esc pressed). You want to append at the end of the current line, regardless of the cursor’s current column. Standard vi/Vim behavior. Concept / Approach: The uppercase command A moves the cursor to end of line and enters insert mode, letting you append immediately. Lowercase a appends after the cursor at its current position, i inserts before the cursor, and I inserts at the first non-blank character of the line. Step-by-Step Solution: Press A in normal mode.The cursor jumps to the last character of the current line.vi switches to insert mode so you can type appended text.Press Esc to return to normal mode when finished. Verification / Alternative check: Try a to see it appends right after the cursor, not at line end. Try I to start typing at the first non-blank, which differs from A’s behavior on indented code lines. Why Other Options Are Wrong: a (Option B) appends after the cursor position only.i (Option C) inserts before the cursor position.I (Option D) inserts at the first non-blank of the line. Common Pitfalls: Forgetting to exit insert mode with Esc. Using a instead of A on long lines, causing mid-line insertions. Confusing I and A in indented code where leading whitespace matters. Final Answer: A

Unix Questions