Brainscape Linux

Question 1

how do you specify a delimiter, also, what is the default delimiter if not specified

Answer 1

-d, –delimiter (e.g. “cut -d ‘,’”) tab is default

Question 2

what are the three ways you can specify what is to be sliced

Answer 2

-b, –bytes -c, –characters -f, –fields

Question 3

how do you select the inverse the fields you specify (e.g. everything but)

Answer 3

–complement

Question 4

how do you ignore any lines that don’t contain the delimiter character

Answer 4

-s, –only-delimited

Question 5

how do you specify a different delimiter for the OUTPUT of what is cut

Answer 5

–output-delimiter=STRING

Question 6

how do you specify the following: from N to end of line from beginning of line to M from N to M columns 2 through four and column 6

Answer 6

N- -M N-M 2-4,6

Question 7

are ranges inclusive or exclusive

Answer 7

ranges are inclusive

Question 8

what do fields begin counting from

Answer 8

fields begin at at “1” for cut

Question 9

using sed, double space a file

Answer 9

sed G

Question 10

using sed, double space a file that already has blank lines in it (the output should have no more than one blank line between lines of text)

Answer 10

sed ‘/^$/d;G’ (delete any lines that meet the address flag of being blank, and double space file)

Question 11

using sed, undo double-spacing (assuming even-numbered lines are always blank)

Answer 11

sed ‘n;d’

Question 12

using sed, convert Unix format (LF) to DOS format (CRLF)

Answer 12

sed ‘s/$/\r/’

Question 13

using sed, delete leading whitespace (tabs, spaces) from beginning of each line

Answer 13

sed ‘s/^[ \t]*//’

Question 14

using sed, delete trailing whitespace (tabs, spaces) from each end of line

Answer 14

sed ‘s/[ \t]*$//’

Question 15

using sed, replace only the first instance in each line

Answer 15

sed ‘s/foo/bar/’

Question 16

using sed, replace only the fourth instance in each line

Answer 16

sed ‘s/foo/bar/4’

Question 17

using sed, replace all instances in a line

Answer 17

sed ‘s/foo/bar/g’

Question 18

using sed, substitute “foo” with “bar” ONLY for lines which contain “baz”

Answer 18

sed ‘/baz/s/foo/bar/g’

Question 19

using sed, substitute “foo” with “bar” EXCEPT for lines which contain “baz”

Answer 19

sed ‘/baz/!s/foo/bar/g’

Question 20

using sed, change “scarlet” or “ruby” or “puce” to “red”

Answer 20

sed ‘s/scarlet|ruby|puce/red/g’

Question 21

using sed, add a blank line every 5 lines (after lines 5, 10, 15, 20, etc.)

Answer 21

sed ‘1~5G’

Question 22

using sed, print the first 10 lines of file (emulate “head”), print the first line of the file

Answer 22

sed 10q (remember that “q” will print the current pattern space before quitting sed q)

Question 23

using sed, print only lines which match regular expression (emulate “grep”)

Answer 23

sed -n ‘/regexp/p’ OR sed ‘/regexp/!d’

Question 24

using sed, print only lines that do NOT match regexp (emulate “grep -v”)

Answer 24

sed -n ‘/regexp/!p’ OR sed ‘/regexp/d’

Question 25

using sed, print all of file EXCEPT section between 2 regular expressions

Answer 25

sed '/Iowa/,/Montana/d'

Question 26

using sed, delete lines matching pattern

Answer 26

sed '/pattern/d'

Question 27

using sed, add a leading angle bracket and space to each line (quote a message)

Answer 27

sed 's/^/> /'

Question 28

using sed, delete leading angle bracket & space from each line (unquote a message)

Answer 28

sed 's/^> //'

Question 29

sed command: q

Answer 29

print current pattern space and quit

Question 30

sed command: d

Answer 30

delete current pattern space and immediately start next cycle

Question 31

sed command: p

Answer 31

print the current pattern space (usually used in conjunction with "-n" option)

Question 32

sed command: n

Answer 32

print pattern space (or not, if auto-print is disabled), and replace the pattern space with the next line of input (mnemonic: "next")

Question 33

sed command: { and }

Answer 33

groups of commands can be enclosed between curly braces--this can be helpful when using addresses for multiple commands

Question 34

sed command: "a text"

Answer 34

append "text" after a line (at the end of the cycle), ignoring leading whitespace (text to add is read to the end of the line)

Question 35

sed command: "i text"

Answer 35

same as "a text", but inserts text BEFORE the line

Question 36

sed command: "c text"

Answer 36

change text (same as "a text", except that this one deletes lines matching the address or address-range, and puts "text" in their place)

Question 37

sed command: =

Answer 37

print the current line number, with a trailing newline

Question 38

sed command: "r filename"

Answer 38

read filename and insert at end of cycle

Question 39

sed command: "w filename"

Answer 39

write the pattern space to filename (file will be created (or overwritten) at the beginning of the script, and all "w" commands pointed to the same filename will be appended to the file throughout the script)

Question 40

sed command: D

Answer 40

delete text in the pattern space up to the first newline, and start a new cycle without reading a new line of input (if only one line in pattern space, works just like lower-case "d")

Question 41

sed command: N

Answer 41

add a newline and append the next line of input to pattern space (no more input, exit without processing any more commands)

Question 42

sed command: P

Answer 42

print pattern space up to the first newline

Question 43

sed command: h

Answer 43

overwrite the hold space with the contents of the pattern space

Question 44

sed command: H

Answer 44

append a newline to hold space and append current pattern space to hold space

Question 45

sed command: g

Answer 45

write the hold space into pattern space (overwrites) (mnemonic: "Go to the pattern space")

Question 46

sed command: G

Answer 46

append newline to pattern space and add contents of hold space

Question 47

sed command: x

Answer 47

swap contents of the hold and pattern spaces

Question 48

sed command: ": label"

Answer 48

create a label for future branch commands

Question 49

sed command: "b label"

Answer 49

branch unconditionally to label; if label is omitted, just start next cycle

Question 50

sed command: "t label"

Answer 50

branch to label only if there has been a successful substitution since the last input line was read or conditional branch was taken (if label is omitted, just start the next cycle)

Question 51

sed command: l (lower-case "L")

Answer 51

unambiguously print the pattern space (useful for debugging)

Question 52

sed command: s///g

Answer 52

search and replace, all matches in line

Question 53

sed command: s///2

Answer 53

replace only the second occurrence in each line

Question 54

sed command: s///p

Answer 54

print the pattern space if the substitution was made

Question 55

sed command: s///w file.txt

Answer 55

write result to file if successful substitution was made (will append subsequent references to the same file)

Question 56

sed command: s///i

Answer 56

make regexp case-insensitive (can be lowercase or uppercase "i")

Question 57

sed command: s///i2w file.txt

Answer 57

You can specify more than one flag (this one will be case-insensitive, sub the second match on a line, and write result to file).

Question 58

sed addressing: delete line three

Answer 58

3d

Question 59

sed addressing: delete last line in stream

Answer 59

$d

Question 60

sed addressing: delete all lines that are NOT the last line

Answer 60

$!d

Question 61

sed addressing: match every "stepth" line, starting with "first"

Answer 61

first~step

Question 62

sed addressing: delete lines matching regexp, also, how to use a different character for regexp addresses

Answer 62

/regexp/d \%regexp%d

Question 63

sed addressing: case-insensitive regexp

Answer 63

/regexp/I (must be uppercase)

Question 64

sed addressing: multi-line mode regexp

Answer 64

/regexp/M (must be uppercase)

Question 65

how to use the delimiter character in a regexp

Answer 65

escape it with a backslash

Question 66

sed addressing: reuse the last-used regexp

Answer 66

use address of "//" (works both for addressing and for the "s" command!)

Question 67

sed addressing: print lines four through six

Answer 67

sed -n '4,6p'

Question 68

what will the following print and why: seq 10 | sed -n '4,/[0-9]/p'

Answer 68

It will print "4" and "5". This is because regular expression matching begins only on the line *after* the first address.

Question 69

sed addressing: match address and the "N" lines following the first address

Answer 69

address,+N e.g. '6,+2' or '/hey/,+2' (address can be either a number or a regular expression)

Question 70

sed options: suppress automatic printing of pattern space

Answer 70

-n, --quiet, --silent

Question 71

sed options: edit file in-place (and make backup if SUFFIX supplied)

Answer 71

-i [SUFFIX], --in-place[=SUFFIX]

Question 72

sed options: use extended regular expressions instead of basic (ERE vs BRE)

Answer 72

-E, -r, --regexp-extended

Question 73

sed options: add a short script of sed commands from the command line

Answer 73

-e (e.g. "sed -e '1d' -e '2s/a/b/'")

Question 74

add the contents of a script file to the commands being executed

Answer 74

-f script-file, --file=script-file

Question 75

what is the difference between BRE and ERE regular expressions

Answer 75

In the POSIX standard, Basic Regular Syntax (BRE) requires that the metacharacters ? + | ( ) and { } and | must be escaped to make them special (e.g. \(\) and \{\}), whereas Extended Regular Syntax (ERE) does not.

Question 76

how to simulate "-n" right from within a Sed script

Answer 76

first two characters in file "#n"

Question 77

using sed, make to work on each file separately (rather than as one continuous stream of concatenated files)

Answer 77

specify the -s, --separate option

Question 78

using sed, convert DOS format (CRLF) to Unix format (LF)

Answer 78

sed 's/\r$//'

Question 79

create a gzip/bzip2/xz compressed archive

Answer 79

tar czvf/cjvf/cJvf compressed.tar.gz/bz2/xz directory

Question 80

peek inside a gzip/bzip2/xz compressed archive

Answer 80

tar tzvf/tjvf/tJvf compressed.tar.gz/bz2/xz

Question 81

extract a gzip/bzip2/xz compressed archive

Answer 81

tar xzvf/xjvf/xJvf compressed.tar.gz/bz2/xz

Question 82

what are the options you can use for compression using tar (short and long)

Answer 82

z --gzip j --bzip2 J --xz

Question 83

tar argument used to specify output archive file name

Answer 83

f FILE, --file=FILE

Question 84

tar function to create a new archive

Answer 84

c, --create

Question 85

tar option to be verbose

Answer 85

v, --verbose

Question 86

tar function to list the contents of an archive

Answer 86

t, --list (mnemonic "Tell me what's in this archive")

Question 87

tar function to extract files from an archive

Answer 87

x, --extract, --get

Question 88

tar function to append other TAR files to an existing archive

Answer 88

A, --catenate, --concatenate

Question 89

tar function to calculate differences between the archive and the file system

Answer 89

d, --diff, --compare

Question 90

tar function to append files to the end of a tar archive

Answer 90

r, --append (mnemonic: "r" is at the end of the word "tar", and this command will append a file to the end of the archive)

Question 91

tar function to append files, but only those that are newer than the copy in the archive

Answer 91

u, --update

Question 92

what is the difference between --append and --update in tar

Answer 92

--append adds the files no matter what, whereas --update only adds them if the files are newer than those in archive

Question 93

tar option to infer type of compression to use based on the file extension you use

Answer 93

-a, --autocompress (or --no-auto-compress to explicitly turn off this behavior)

Question 94

tar option to exclude certain files or folders from the backup

Answer 94

--exclude=PATTERN (patterns are case sensitive by default; use --ignore-case to change this)

Question 95

tar option to exclude version control system directories

Answer 95

--exclude-vcs

Question 96

tar option to explicitly *not* overwrite existing files when extracting

Answer 96

k, --keep-old-files

Question 97

tar option to not overwrite any files that are newer than the archived copies (when extracting)

Answer 97

--keep-newer-files

Question 98

tar option to display its default options

Answer 98

--show-default

Question 99

tar option to exclude files and patterns LISTED IN A FILE instead of from command line

Answer 99

-X, --exclude-from=FILE

Question 100

when listing or extracting with tar, list each directory that does *not* match search criteria

Answer 100

--show-omitted-dirs

Question 101

how to replace a file in an archive with a different copy

Answer 101

delete the file first using "tar --delete --file=archive.tar file1", then use append to add the new file (tar does not delete any files from archive automatically)

Question 102

what is the basic tar syntax

Answer 102

tar {function} [options] [pathname ...] (e.g. tar af archive.tar fileone.txt filetwo.txt), so one of the tar functions (e.g. --create, --update, --extract, etc.) has to be first in line for your arguments