Week 8 Flashcards

Question

What does sed do?

Answer 1

stream editor, reads from a stdin or a file ,and writes to stdout editing one line at a time from a given edit script

Answer 2

replaces every foo with bar globally. if the g wasnt there, it would only do the first match.

Answer 3

-d : sets the delimited to :. and -f 7 picks out the svent field

Answer 4

Abstract layer about secondary storage. i.e., users interact with files and directories but the actual representation fo storage is left to OS. It' responsible for allocating space on secondary stages.

Answer 5

places the replacement value exactly where the & is ex: sed -e 's/xyz*y/--&-- /' infile: the xyzzy fell = the --xyzzy-- fell

Answer 6

translates characters in input to output (only uses stdin -> stdout, need redirection to use files) ex: echo "hello world" | tr 'a-z' 'A-Z' = HELLO WORLD

Answer 7

put it in the string o.e., sed -e '5,7 s/a/b/' only replaces lines 5-7 a's with b's

Answer 8

Substitutes the XXX with the value of var1 in the embedded document Here document (embedded document)

Answer 9

Name, identifier, type, location, size, protection, time, date, user identification

Answer 10

A way of accessing file information directly through the use of a known location or block, without needing to process previous data.

Answer 11

a technique that involves storing records in blocks of a file or database. each record is associated with a key.

Answer 12

Sequential, direct access, indexed access

Answer 13

A way of organizing files in a hierarchical format, where directories can contain files ando ther subdirectories. It mapes file names to physical storage locations, and supports various operations.

Answer 14

an improvement on a persistent B tree. It notably: Keeps nodes more full by redistributing keys between nodes more aggresively, holds more child pointers per nodes

Answer 15

A self balancing search tree used in filesystems and databases. Each node contains multiple keys and child pointers. All changes are non destructive (it creates a new version of the tree each edit)

Answer 16

The top level of the disk is a directory, second level is made up of user directories + 1 directory for sys commands

Answer 17

More than one path or a dir or a file

Answer 18

Files can be shared, directories cant

Answer 19

A file with special attributes that contains the path to a real file or dir

Answer 20

a subset of the disk

Answer 21

First 512 byte block was the legacy MBR, and the rest of the disk was divided into at most 4 primary partitions, with however many sub partitions as necessary

Answer 22

GPT header, partition table 31 blocks 2-33, secondary GPT header, Protective MBR,

Answer 23

It consisted of a partition table and a boot code (446 bytes)

Answer 24

Holds pointers to the partition tables first and last usable block

Answer 25

Holds records on where each partition sits in memory, boot information and meta data

Answer 26

prevents the legacy systems from corrupting the rest of the disk. Holds one partition of unknown type

Answer 27

Incase the first one becomes corrupted

Answer 28

One of the partitions in the GUID, it has it's own file system format and contains info on HOW to boot the system. i.e., if we have a linux & windows partition, the EFI contasin enough space for the bootcode to load each one.

Answer 29

Hubert smell's like he looks. Silly. Block containing code to start the OS. Not big enough to hold the actual OS.

Answer 30

Controls the contents of the partition. It can free lists, counters dates, etc. The first block of the partition (usually) and holds the list of free blocks that are available.

Answer 31

one for each file, contains info such as file id, owner, size, aTimes and the location of the data blocks. In linux, its referred to as an inode.

Answer 32

Reads the PCB and sets up internal data structures such as buffers etc. Then stores it in the mount table.

Answer 33

A designated space on a storage device used by the OS as virtual memory. Essentially provides extra VM by using disk space when physical ram is full.

Answer 34

Logical file system (Dir structure, prot, perms) File organization (logical block management Basic File System (reads and writes blocks) I/O Control Devices

Answer 35

It's essentially the top level directory or root directory of your mounted device. Any directory can hold a mount point. example: /huberts-CP-device/....

Answer 36

holds info about each mounted partition, and the file system inside of it

Answer 37

Holds a reference to the system wide file table, and the current file position for this process. It's necessary for each file so one process doesn't pick up from the end what another process started.

Answer 38

Holds info from each FCB on every open file.

Answer 39

- Search the directory structure (could be cached in mem) for the file identifier - See if the FCB is already in memory (System file table), copy into memory if its not and inc counter ( counter = num processes accessing ) - Allocate entry in process file table. Point to the systme file table, allocate bufffers and initialize the current file poistion - return a pointer or index to process FCB

Answer 40

- use pointer or index to access the process's FCB - decrement counter. If counter is 0 (last process with file open), mark the FCB for deletion - Free process FCB

Answer 41

The data blocks for a file are stored next to each other on the disk

Answer 42

Instead of storing data blocks directly, the system uses index blocks that hold pointers to the actual data blocks of the files.

Answer 43

Holds general information such as the filetype, permissions, owner, group size Holds 12 direct pointers to data blocks. Holds 3 "indirect" pointers to other tables for indirect data block management.

Answer 44

Each files blocks are not stored together, but instead each block points to the next block in the file Uses a FAT (file allocation table) to store the pointers. *FAT groups blocks into clusters, and the table is kept in memory.