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What does the command `sha384sum` do? | sha384sum - compute and check SHA384 message digest |
How is the `sha384sum` used? | sha384sum [OPTION]... [FILE]... |
What is the detailed desciption of the `sha384sum`? | Print or check SHA384 (384-bit) checksums.
With no FILE, or when FILE is -, read standard input.
-b, --binary
read in binary mode
-c, --check
read checksums from the FILEs and check them
--tag create a BSD-style checksum
-t, --text
read in text mode (default)
-z, --zero
end each output line with NUL, not newline, and disable file name escaping
The following five options are useful only when verifying checksums:
--ignore-missing
don't fail or report status for missing files
--quiet
don't print OK for each successfully verified file
--status
don't output anything, status code shows success
--strict
exit non-zero for improperly formatted checksum lines
-w, --warn
warn about improperly formatted checksum lines
--help display this help and exit
--version
output version information and exit
The sums are computed as described in FIPS-180-2. When checking, the input should be a former output of this
program. The default mode is to print a line with: checksum, a space, a character indicating input mode ('*'
for binary, ' ' for text or where binary is insignificant), and name for each FILE.
Note: There is no difference between binary mode and text mode on GNU systems. |
What does the command `realpath` do? | realpath - print the resolved path |
How is the `realpath` used? | realpath [OPTION]... FILE... |
What is the detailed desciption of the `realpath`? | Print the resolved absolute file name; all but the last component must exist
-e, --canonicalize-existing
all components of the path must exist
-m, --canonicalize-missing
no path components need exist or be a directory
-L, --logical
resolve '..' components before symlinks
-P, --physical
resolve symlinks as encountered (default)
-q, --quiet
suppress most error messages
--relative-to=DIR
print the resolved path relative to DIR
--relative-base=DIR
print absolute paths unless paths below DIR
-s, --strip, --no-symlinks
don't expand symlinks
-z, --zero
end each output line with NUL, not newline
--help display this help and exit
--version
output version information and exit |
What does the command `expr` do? | expr - evaluate expressions |
How is the `expr` used? | expr EXPRESSION
expr OPTION |
What is the detailed desciption of the `expr`? | --help display this help and exit
--version
output version information and exit
Print the value of EXPRESSION to standard output. A blank line below separates increasing precedence groups.
EXPRESSION may be:
ARG1 | ARG2
ARG1 if it is neither null nor 0, otherwise ARG2
ARG1 & ARG2
ARG1 if neither argument is null or 0, otherwise 0
ARG1 < ARG2
ARG1 is less than ARG2
ARG1 <= ARG2
ARG1 is less than or equal to ARG2
ARG1 = ARG2
ARG1 is equal to ARG2
ARG1 != ARG2
ARG1 is unequal to ARG2
ARG1 >= ARG2
ARG1 is greater than or equal to ARG2
ARG1 > ARG2
ARG1 is greater than ARG2
ARG1 + ARG2
arithmetic sum of ARG1 and ARG2
ARG1 - ARG2
arithmetic difference of ARG1 and ARG2
ARG1 * ARG2
arithmetic product of ARG1 and ARG2
ARG1 / ARG2
arithmetic quotient of ARG1 divided by ARG2
ARG1 % ARG2
arithmetic remainder of ARG1 divided by ARG2
STRING : REGEXP
anchored pattern match of REGEXP in STRING
match STRING REGEXP
same as STRING : REGEXP
substr STRING POS LENGTH
substring of STRING, POS counted from 1
index STRING CHARS
index in STRING where any CHARS is found, or 0
length STRING
length of STRING
+ TOKEN
interpret TOKEN as a string, even if it is a
keyword like 'match' or an operator like '/'
( EXPRESSION )
value of EXPRESSION
Beware that many operators need to be escaped or quoted for shells. Comparisons are arithmetic if both ARGs are
numbers, else lexicographical. Pattern matches return the string matched between \( and \) or null; if \( and
\) are not used, they return the number of characters matched or 0.
Exit status is 0 if EXPRESSION is neither null nor 0, 1 if EXPRESSION is null or 0, 2 if EXPRESSION is syntacti‐
cally invalid, and 3 if an error occurred. |
What does the command `wc` do? | wc - print newline, word, and byte counts for each file |
How is the `wc` used? | wc [OPTION]... [FILE]...
wc [OPTION]... --files0-from=F |
What is the detailed desciption of the `wc`? | Print newline, word, and byte counts for each FILE, and a total line if more than one FILE is specified. A word
is a non-zero-length sequence of printable characters delimited by white space.
With no FILE, or when FILE is -, read standard input.
The options below may be used to select which counts are printed, always in the following order: newline, word,
character, byte, maximum line length.
-c, --bytes
print the byte counts
-m, --chars
print the character counts
-l, --lines
print the newline counts
--files0-from=F
read input from the files specified by NUL-terminated names in file F; If F is - then read names from
standard input
-L, --max-line-length
print the maximum display width
-w, --words
print the word counts
--total=WHEN
when to print a line with total counts; WHEN can be: auto, always, only, never
--help display this help and exit
--version
output version information and exit |
What does the command `nproc` do? | nproc - print the number of processing units available |
How is the `nproc` used? | nproc [OPTION]... |
What is the detailed desciption of the `nproc`? | Print the number of processing units available to the current process, which may be less than the number of on‐
line processors
--all print the number of installed processors
--ignore=N
if possible, exclude N processing units
--help display this help and exit
--version
output version information and exit |
What does the command `fold` do? | fold - wrap each input line to fit in specified width |
How is the `fold` used? | fold [OPTION]... [FILE]... |
What is the detailed desciption of the `fold`? | Wrap input lines in each FILE, writing to standard output.
With no FILE, or when FILE is -, read standard input.
Mandatory arguments to long options are mandatory for short options too.
-b, --bytes
count bytes rather than columns
-s, --spaces
break at spaces
-w, --width=WIDTH
use WIDTH columns instead of 80
--help display this help and exit
--version
output version information and exit |
What does the command `logname` do? | logname - print user´s login name |
How is the `logname` used? | logname [OPTION] |
What is the detailed desciption of the `logname`? | Print the user's login name.
--help display this help and exit
--version
output version information and exit |
What does the command `expand` do? | expand - convert tabs to spaces |
How is the `expand` used? | expand [OPTION]... [FILE]... |
What is the detailed desciption of the `expand`? | Convert tabs in each FILE to spaces, writing to standard output.
With no FILE, or when FILE is -, read standard input.
Mandatory arguments to long options are mandatory for short options too.
-i, --initial
do not convert tabs after non blanks
-t, --tabs=N
have tabs N characters apart, not 8
-t, --tabs=LIST
use comma separated list of tab positions. The last specified position can be prefixed with '/' to spec‐
ify a tab size to use after the last explicitly specified tab stop. Also a prefix of '+' can be used to
align remaining tab stops relative to the last specified tab stop instead of the first column
--help display this help and exit
--version
output version information and exit |
What does the command `uptime` do? | uptime - Tell how long the system has been running. |
How is the `uptime` used? | uptime [options] |
What is the detailed desciption of the `uptime`? | uptime gives a one line display of the following information. The current time, how long the system has been
running, how many users are currently logged on, and the system load averages for the past 1, 5, and 15 minutes.
This is the same information contained in the header line displayed by w(1).
System load averages is the average number of processes that are either in a runnable or uninterruptable state.
A process in a runnable state is either using the CPU or waiting to use the CPU. A process in uninterruptable
state is waiting for some I/O access, eg waiting for disk. The averages are taken over the three time inter‐
vals. Load averages are not normalized for the number of CPUs in a system, so a load average of 1 means a sin‐
gle CPU system is loaded all the time while on a 4 CPU system it means it was idle 75% of the time. |
What does the command `md5sum` do? | md5sum - compute and check MD5 message digest |
How is the `md5sum` used? | md5sum [OPTION]... [FILE]... |
What is the detailed desciption of the `md5sum`? | Print or check MD5 (128-bit) checksums.
With no FILE, or when FILE is -, read standard input.
-b, --binary
read in binary mode
-c, --check
read checksums from the FILEs and check them
--tag create a BSD-style checksum
-t, --text
read in text mode (default)
-z, --zero
end each output line with NUL, not newline, and disable file name escaping
The following five options are useful only when verifying checksums:
--ignore-missing
don't fail or report status for missing files
--quiet
don't print OK for each successfully verified file
--status
don't output anything, status code shows success
--strict
exit non-zero for improperly formatted checksum lines
-w, --warn
warn about improperly formatted checksum lines
--help display this help and exit
--version
output version information and exit
The sums are computed as described in RFC 1321. When checking, the input should be a former output of this pro‐
gram. The default mode is to print a line with: checksum, a space, a character indicating input mode ('*' for
binary, ' ' for text or where binary is insignificant), and name for each FILE.
Note: There is no difference between binary mode and text mode on GNU systems. |
What does the command `dd` do? | dd - convert and copy a file |
How is the `dd` used? | dd [OPERAND]...
dd OPTION |
What is the detailed desciption of the `dd`? | Copy a file, converting and formatting according to the operands.
bs=BYTES
read and write up to BYTES bytes at a time (default: 512); overrides ibs and
obs
cbs=BYTES
convert BYTES bytes at a time
conv=CONVS
convert the file as per the comma separated symbol list
count=N
copy only N input blocks
ibs=BYTES
read up to BYTES bytes at a time (default: 512)
if=FILE
read from FILE instead of stdin
iflag=FLAGS
read as per the comma separated symbol list
obs=BYTES
write BYTES bytes at a time (default: 512)
of=FILE
write to FILE instead of stdout
oflag=FLAGS
write as per the comma separated symbol list
seek=N (or oseek=N) skip N obs-sized output blocks
skip=N (or iseek=N) skip N ibs-sized input blocks
status=LEVEL
The LEVEL of information to print to stderr; 'none' suppresses everything but
error messages, 'noxfer' suppresses the final transfer statistics, 'progress'
shows periodic transfer statistics
N and BYTES may be followed by the following multiplicative suffixes: c=1, w=2,
b=512, kB=1000, K=1024, MB=1000*1000, M=1024*1024, xM=M, GB=1000*1000*1000,
G=1024*1024*1024, and so on for T, P, E, Z, Y, R, Q. Binary prefixes can be used,
too: KiB=K, MiB=M, and so on. If N ends in 'B', it counts bytes not blocks.
Each CONV symbol may be:
ascii from EBCDIC to ASCII
ebcdic from ASCII to EBCDIC
ibm from ASCII to alternate EBCDIC
block pad newline-terminated records with spaces to cbs-size
unblock
replace trailing spaces in cbs-size records with newline
lcase change upper case to lower case
ucase change lower case to upper case
sparse try to seek rather than write all-NUL output blocks
swab swap every pair of input bytes
sync pad every input block with NULs to ibs-size; when used with block or unblock,
pad with spaces rather than NULs
excl fail if the output file already exists
nocreat
do not create the output file
notrunc
do not truncate the output file
noerror
continue after read errors
fdatasync
physically write output file data before finishing
fsync likewise, but also write metadata
Each FLAG symbol may be:
append append mode (makes sense only for output; conv=notrunc suggested)
direct use direct I/O for data
directory
fail unless a directory
dsync use synchronized I/O for data
sync likewise, but also for metadata
fullblock
accumulate full blocks of input (iflag only)
nonblock
use non-blocking I/O
noatime
do not update access time
nocache
Request to drop cache. See also oflag=sync
noctty do not assign controlling terminal from file
nofollow
do not follow symlinks
Sending a USR1 signal to a running 'dd' process makes it print I/O statistics to
standard error and then resume copying.
Options are:
--help display this help and exit
--version
output version information and exit |
What does the command `mknod` do? | mknod - make block or character special files |
How is the `mknod` used? | mknod [OPTION]... NAME TYPE [MAJOR MINOR] |
What is the detailed desciption of the `mknod`? | Create the special file NAME of the given TYPE.
Mandatory arguments to long options are mandatory for short options too.
-m, --mode=MODE
set file permission bits to MODE, not a=rw - umask
-Z set the SELinux security context to default type
--context[=CTX]
like -Z, or if CTX is specified then set the SELinux or SMACK security context to CTX
--help display this help and exit
--version
output version information and exit
Both MAJOR and MINOR must be specified when TYPE is b, c, or u, and they must be omitted when TYPE is p. If MA‐
JOR or MINOR begins with 0x or 0X, it is interpreted as hexadecimal; otherwise, if it begins with 0, as octal;
otherwise, as decimal. TYPE may be:
b create a block (buffered) special file
c, u create a character (unbuffered) special file
p create a FIFO
NOTE: your shell may have its own version of mknod, which usually supersedes the version described here. Please
refer to your shell's documentation for details about the options it supports. |
What does the command `unlink` do? | unlink - call the unlink function to remove the specified file |
How is the `unlink` used? | unlink FILE
unlink OPTION |
What is the detailed desciption of the `unlink`? | Call the unlink function to remove the specified FILE.
--help display this help and exit
--version
output version information and exit |
What does the command `[` do? | test - check file types and compare values |
How is the `[` used? | test EXPRESSION
test
[ EXPRESSION ]
[ ]
[ OPTION |
What is the detailed desciption of the `[`? | Exit with the status determined by EXPRESSION.
--help display this help and exit
--version
output version information and exit
An omitted EXPRESSION defaults to false. Otherwise, EXPRESSION is true or false and sets exit status. It is
one of:
( EXPRESSION )
EXPRESSION is true
! EXPRESSION
EXPRESSION is false
EXPRESSION1 -a EXPRESSION2
both EXPRESSION1 and EXPRESSION2 are true
EXPRESSION1 -o EXPRESSION2
either EXPRESSION1 or EXPRESSION2 is true
-n STRING
the length of STRING is nonzero
STRING equivalent to -n STRING
-z STRING
the length of STRING is zero
STRING1 = STRING2
the strings are equal
STRING1 != STRING2
the strings are not equal
INTEGER1 -eq INTEGER2
INTEGER1 is equal to INTEGER2
INTEGER1 -ge INTEGER2
INTEGER1 is greater than or equal to INTEGER2
INTEGER1 -gt INTEGER2
INTEGER1 is greater than INTEGER2
INTEGER1 -le INTEGER2
INTEGER1 is less than or equal to INTEGER2
INTEGER1 -lt INTEGER2
INTEGER1 is less than INTEGER2
INTEGER1 -ne INTEGER2
INTEGER1 is not equal to INTEGER2
FILE1 -ef FILE2
FILE1 and FILE2 have the same device and inode numbers
FILE1 -nt FILE2
FILE1 is newer (modification date) than FILE2
FILE1 -ot FILE2
FILE1 is older than FILE2
-b FILE
FILE exists and is block special
-c FILE
FILE exists and is character special
-d FILE
FILE exists and is a directory
-e FILE
FILE exists
-f FILE
FILE exists and is a regular file
-g FILE
FILE exists and is set-group-ID
-G FILE
FILE exists and is owned by the effective group ID
-h FILE
FILE exists and is a symbolic link (same as -L)
-k FILE
FILE exists and has its sticky bit set
-L FILE
FILE exists and is a symbolic link (same as -h)
-N FILE
FILE exists and has been modified since it was last read
-O FILE
FILE exists and is owned by the effective user ID
-p FILE
FILE exists and is a named pipe
-r FILE
FILE exists and the user has read access
-s FILE
FILE exists and has a size greater than zero
-S FILE
FILE exists and is a socket
-t FD file descriptor FD is opened on a terminal
-u FILE
FILE exists and its set-user-ID bit is set
-w FILE
FILE exists and the user has write access
-x FILE
FILE exists and the user has execute (or search) access
Except for -h and -L, all FILE-related tests dereference symbolic links. Beware that parentheses need to be es‐
caped (e.g., by backslashes) for shells. INTEGER may also be -l STRING, which evaluates to the length of
STRING.
NOTE: Binary -a and -o are inherently ambiguous. Use 'test EXPR1 && test EXPR2' or 'test EXPR1 || test EXPR2'
instead.
NOTE: [ honors the --help and --version options, but test does not. test treats each of those as it treats any
other nonempty STRING.
NOTE: your shell may have its own version of test and/or [, which usually supersedes the version described here.
Please refer to your shell's documentation for details about the options it supports. |
What does the command `chown` do? | chown - change file owner and group |
How is the `chown` used? | chown [OPTION]... [OWNER][:[GROUP]] FILE...
chown [OPTION]... --reference=RFILE FILE... |
What is the detailed desciption of the `chown`? | This manual page documents the GNU version of chown. chown changes the user and/or
group ownership of each given file. If only an owner (a user name or numeric user
ID) is given, that user is made the owner of each given file, and the files' group
is not changed. If the owner is followed by a colon and a group name (or numeric
group ID), with no spaces between them, the group ownership of the files is changed
as well. If a colon but no group name follows the user name, that user is made the
owner of the files and the group of the files is changed to that user's login group.
If the colon and group are given, but the owner is omitted, only the group of the
files is changed; in this case, chown performs the same function as chgrp. If only
a colon is given, or if the entire operand is empty, neither the owner nor the group
is changed. |
What does the command `basename` do? | basename - strip directory and suffix from filenames |
How is the `basename` used? | basename NAME [SUFFIX]
basename OPTION... NAME... |
What is the detailed desciption of the `basename`? | Print NAME with any leading directory components removed. If specified, also remove a trailing SUFFIX.
Mandatory arguments to long options are mandatory for short options too.
-a, --multiple
support multiple arguments and treat each as a NAME
-s, --suffix=SUFFIX
remove a trailing SUFFIX; implies -a
-z, --zero
end each output line with NUL, not newline
--help display this help and exit
--version
output version information and exit |
What does the command `pr` do? | pr - convert text files for printing |
How is the `pr` used? | pr [OPTION]... [FILE]... |
What is the detailed desciption of the `pr`? | Paginate or columnate FILE(s) for printing.
With no FILE, or when FILE is -, read standard input.
Mandatory arguments to long options are mandatory for short options too.
+FIRST_PAGE[:LAST_PAGE], --pages=FIRST_PAGE[:LAST_PAGE]
begin [stop] printing with page FIRST_[LAST_]PAGE
-COLUMN, --columns=COLUMN
output COLUMN columns and print columns down, unless -a is used. Balance number of lines in the columns
on each page
-a, --across
print columns across rather than down, used together with -COLUMN
-c, --show-control-chars
use hat notation (^G) and octal backslash notation
-d, --double-space
double space the output
-D, --date-format=FORMAT
use FORMAT for the header date
-e[CHAR[WIDTH]], --expand-tabs[=CHAR[WIDTH]]
expand input CHARs (TABs) to tab WIDTH (8)
-F, -f, --form-feed
use form feeds instead of newlines to separate pages (by a 3-line page header with -F or a 5-line header
and trailer without -F)
-h, --header=HEADER
use a centered HEADER instead of filename in page header, -h "" prints a blank line, don't use -h""
-i[CHAR[WIDTH]], --output-tabs[=CHAR[WIDTH]]
replace spaces with CHARs (TABs) to tab WIDTH (8)
-J, --join-lines
merge full lines, turns off -W line truncation, no column alignment, --sep-string[=STRING] sets separa‐
tors
-l, --length=PAGE_LENGTH
set the page length to PAGE_LENGTH (66) lines (default number of lines of text 56, and with -F 63). im‐
plies -t if PAGE_LENGTH <= 10
-m, --merge
print all files in parallel, one in each column, truncate lines, but join lines of full length with -J
-n[SEP[DIGITS]], --number-lines[=SEP[DIGITS]]
number lines, use DIGITS (5) digits, then SEP (TAB), default counting starts with 1st line of input file
-N, --first-line-number=NUMBER
start counting with NUMBER at 1st line of first page printed (see +FIRST_PAGE)
-o, --indent=MARGIN
offset each line with MARGIN (zero) spaces, do not affect -w or -W, MARGIN will be added to PAGE_WIDTH
-r, --no-file-warnings
omit warning when a file cannot be opened
-s[CHAR], --separator[=CHAR]
separate columns by a single character, default for CHAR is the <TAB> character without -w and 'no char'
with -w. -s[CHAR] turns off line truncation of all 3 column options (-COLUMN|-a -COLUMN|-m) except -w is
set
-S[STRING], --sep-string[=STRING]
separate columns by STRING, without -S: Default separator <TAB> with -J and <space> otherwise (same as
-S" "), no effect on column options
-t, --omit-header
omit page headers and trailers; implied if PAGE_LENGTH <= 10
-T, --omit-pagination
omit page headers and trailers, eliminate any pagination by form feeds set in input files
-v, --show-nonprinting
use octal backslash notation
-w, --width=PAGE_WIDTH
set page width to PAGE_WIDTH (72) characters for multiple text-column output only, -s[char] turns off
(72)
-W, --page-width=PAGE_WIDTH
set page width to PAGE_WIDTH (72) characters always, truncate lines, except -J option is set, no inter‐
ference with -S or -s
--help display this help and exit
--version
output version information and exit |
What does the command `fmt` do? | fmt - simple optimal text formatter |
How is the `fmt` used? | fmt [-WIDTH] [OPTION]... [FILE]... |
What is the detailed desciption of the `fmt`? | Reformat each paragraph in the FILE(s), writing to standard output. The option -WIDTH is an abbreviated form of
--width=DIGITS.
With no FILE, or when FILE is -, read standard input.
Mandatory arguments to long options are mandatory for short options too.
-c, --crown-margin
preserve indentation of first two lines
-p, --prefix=STRING
reformat only lines beginning with STRING, reattaching the prefix to reformatted lines
-s, --split-only
split long lines, but do not refill
-t, --tagged-paragraph
indentation of first line different from second
-u, --uniform-spacing
one space between words, two after sentences
-w, --width=WIDTH
maximum line width (default of 75 columns)
-g, --goal=WIDTH
goal width (default of 93% of width)
--help display this help and exit
--version
output version information and exit |
What does the command `who` do? | who - show who is logged on |
How is the `who` used? | who [OPTION]... [ FILE | ARG1 ARG2 ] |
What is the detailed desciption of the `who`? | Print information about users who are currently logged in.
-a, --all
same as -b -d --login -p -r -t -T -u
-b, --boot
time of last system boot
-d, --dead
print dead processes
-H, --heading
print line of column headings
-l, --login
print system login processes
--lookup
attempt to canonicalize hostnames via DNS
-m only hostname and user associated with stdin
-p, --process
print active processes spawned by init
-q, --count
all login names and number of users logged on
-r, --runlevel
print current runlevel
-s, --short
print only name, line, and time (default)
-t, --time
print last system clock change
-T, -w, --mesg
add user's message status as +, - or ?
-u, --users
list users logged in
--message
same as -T
--writable
same as -T
--help display this help and exit
--version
output version information and exit
If FILE is not specified, use /var/run/utmp. /var/log/wtmp as FILE is common. If ARG1 ARG2 given, -m presumed:
'am i' or 'mom likes' are usual. |
What does the command `id` do? | id - print real and effective user and group IDs |
How is the `id` used? | id [OPTION]... [USER]... |
What is the detailed desciption of the `id`? | Print user and group information for each specified USER, or (when USER omitted) for the current process.
-a ignore, for compatibility with other versions
-Z, --context
print only the security context of the process
-g, --group
print only the effective group ID
-G, --groups
print all group IDs
-n, --name
print a name instead of a number, for -ugG
-r, --real
print the real ID instead of the effective ID, with -ugG
-u, --user
print only the effective user ID
-z, --zero
delimit entries with NUL characters, not whitespace;
not permitted in default format
--help display this help and exit
--version
output version information and exit
Without any OPTION, print some useful set of identified information. |
What does the command `mkdir` do? | mkdir - make directories |
How is the `mkdir` used? | mkdir [OPTION]... DIRECTORY... |
What is the detailed desciption of the `mkdir`? | Create the DIRECTORY(ies), if they do not already exist.
Mandatory arguments to long options are mandatory for short options too.
-m, --mode=MODE
set file mode (as in chmod), not a=rwx - umask
-p, --parents
no error if existing, make parent directories as needed, with their file modes unaffected by any -m op‐
tion.
-v, --verbose
print a message for each created directory
-Z set SELinux security context of each created directory to the default type
--context[=CTX]
like -Z, or if CTX is specified then set the SELinux or SMACK security context to CTX
--help display this help and exit
--version
output version information and exit |
What does the command `head` do? | head - output the first part of files |
How is the `head` used? | head [OPTION]... [FILE]... |
What is the detailed desciption of the `head`? | Print the first 10 lines of each FILE to standard output. With more than one FILE, precede each with a header
giving the file name.
With no FILE, or when FILE is -, read standard input.
Mandatory arguments to long options are mandatory for short options too.
-c, --bytes=[-]NUM
print the first NUM bytes of each file; with the leading '-', print all but the last NUM bytes of each
file
-n, --lines=[-]NUM
print the first NUM lines instead of the first 10; with the leading '-', print all but the last NUM lines
of each file
-q, --quiet, --silent
never print headers giving file names
-v, --verbose
always print headers giving file names
-z, --zero-terminated
line delimiter is NUL, not newline
--help display this help and exit
--version
output version information and exit
NUM may have a multiplier suffix: b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024, GB 1000*1000*1000, G
1024*1024*1024, and so on for T, P, E, Z, Y, R, Q. Binary prefixes can be used, too: KiB=K, MiB=M, and so on. |
What does the command `date` do? | date - print or set the system date and time |
How is the `date` used? | date [OPTION]... [+FORMAT]
date [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]] |
What is the detailed desciption of the `date`? | Display date and time in the given FORMAT. With -s, or with [MMDDhhmm[[CC]YY][.ss]], set the date and time.
Mandatory arguments to long options are mandatory for short options too.
-d, --date=STRING
display time described by STRING, not 'now'
--debug
annotate the parsed date, and warn about questionable usage to stderr
-f, --file=DATEFILE
like --date; once for each line of DATEFILE
-I[FMT], --iso-8601[=FMT]
output date/time in ISO 8601 format. FMT='date' for date only (the default), 'hours', 'minutes', 'sec‐
onds', or 'ns' for date and time to the indicated precision. Example: 2006-08-14T02:34:56-06:00
--resolution
output the available resolution of timestamps Example: 0.000000001
-R, --rfc-email
output date and time in RFC 5322 format. Example: Mon, 14 Aug 2006 02:34:56 -0600
--rfc-3339=FMT
output date/time in RFC 3339 format. FMT='date', 'seconds', or 'ns' for date and time to the indicated
precision. Example: 2006-08-14 02:34:56-06:00
-r, --reference=FILE
display the last modification time of FILE
-s, --set=STRING
set time described by STRING
-u, --utc, --universal
print or set Coordinated Universal Time (UTC)
--help display this help and exit
--version
output version information and exit
All options that specify the date to display are mutually exclusive. I.e.: --date, --file, --reference, --reso‐
lution.
FORMAT controls the output. Interpreted sequences are:
%% a literal %
%a locale's abbreviated weekday name (e.g., Sun)
%A locale's full weekday name (e.g., Sunday)
%b locale's abbreviated month name (e.g., Jan)
%B locale's full month name (e.g., January)
%c locale's date and time (e.g., Thu Mar 3 23:05:25 2005)
%C century; like %Y, except omit last two digits (e.g., 20)
%d day of month (e.g., 01)
%D date; same as %m/%d/%y
%e day of month, space padded; same as %_d
%F full date; like %+4Y-%m-%d
%g last two digits of year of ISO week number (see %G)
%G year of ISO week number (see %V); normally useful only with %V
%h same as %b
%H hour (00..23)
%I hour (01..12)
%j day of year (001..366)
%k hour, space padded ( 0..23); same as %_H
%l hour, space padded ( 1..12); same as %_I
%m month (01..12)
%M minute (00..59)
%n a newline
%N nanoseconds (000000000..999999999)
%p locale's equivalent of either AM or PM; blank if not known
%P like %p, but lower case
%q quarter of year (1..4)
%r locale's 12-hour clock time (e.g., 11:11:04 PM)
%R 24-hour hour and minute; same as %H:%M
%s seconds since the Epoch (1970-01-01 00:00 UTC)
%S second (00..60)
%t a tab
%T time; same as %H:%M:%S
%u day of week (1..7); 1 is Monday
%U week number of year, with Sunday as first day of week (00..53)
%V ISO week number, with Monday as first day of week (01..53)
%w day of week (0..6); 0 is Sunday
%W week number of year, with Monday as first day of week (00..53)
%x locale's date representation (e.g., 12/31/99)
%X locale's time representation (e.g., 23:13:48)
%y last two digits of year (00..99)
%Y year
%z +hhmm numeric time zone (e.g., -0400)
%:z +hh:mm numeric time zone (e.g., -04:00)
%::z +hh:mm:ss numeric time zone (e.g., -04:00:00)
%:::z numeric time zone with : to necessary precision (e.g., -04, +05:30)
%Z alphabetic time zone abbreviation (e.g., EDT)
By default, date pads numeric fields with zeroes. The following optional flags may follow '%':
- (hyphen) do not pad the field
_ (underscore) pad with spaces
0 (zero) pad with zeros
+ pad with zeros, and put '+' before future years with >4 digits
^ use upper case if possible
# use opposite case if possible
After any flags comes an optional field width, as a decimal number; then an optional modifier, which is either E
to use the locale's alternate representations if available, or O to use the locale's alternate numeric symbols
if available. |
What does the command `sync` do? | sync - Synchronize cached writes to persistent storage |
How is the `sync` used? | sync [OPTION] [FILE]... |
What is the detailed desciption of the `sync`? | Synchronize cached writes to persistent storage
If one or more files are specified, sync only them, or their containing file systems.
-d, --data
sync only file data, no unneeded metadata
-f, --file-system
sync the file systems that contain the files
--help display this help and exit
--version
output version information and exit |
What does the command `nohup` do? | nohup - run a command immune to hangups, with output to a non-tty |
How is the `nohup` used? | nohup COMMAND [ARG]...
nohup OPTION |
What is the detailed desciption of the `nohup`? | Run COMMAND, ignoring hangup signals.
--help display this help and exit
--version
output version information and exit
If standard input is a terminal, redirect it from an unreadable file. If standard output is a terminal, append
output to 'nohup.out' if possible, '$HOME/nohup.out' otherwise. If standard error is a terminal, redirect it to
standard output. To save output to FILE, use 'nohup COMMAND > FILE'.
NOTE: your shell may have its own version of nohup, which usually supersedes the version described here. Please
refer to your shell's documentation for details about the options it supports.
Exit status:
125 if the nohup command itself fails
126 if COMMAND is found but cannot be invoked
127 if COMMAND cannot be found
- the exit status of COMMAND otherwise |
What does the command `ls` do? | ls - list directory contents |
How is the `ls` used? | ls [OPTION]... [FILE]... |
What is the detailed desciption of the `ls`? | List information about the FILEs (the current directory by default). Sort entries alphabetically if none of
-cftuvSUX nor --sort is specified.
Mandatory arguments to long options are mandatory for short options too.
-a, --all
do not ignore entries starting with .
-A, --almost-all
do not list implied . and ..
--author
with -l, print the author of each file
-b, --escape
print C-style escapes for nongraphic characters
--block-size=SIZE
with -l, scale sizes by SIZE when printing them; e.g., '--block-size=M'; see SIZE format below
-B, --ignore-backups
do not list implied entries ending with ~
-c with -lt: sort by, and show, ctime (time of last change of file status information); with -l: show ctime
and sort by name; otherwise: sort by ctime, newest first
-C list entries by columns
--color[=WHEN]
color the output WHEN; more info below
-d, --directory
list directories themselves, not their contents
-D, --dired
generate output designed for Emacs' dired mode
-f list all entries in directory order
-F, --classify[=WHEN]
append indicator (one of */=>@|) to entries WHEN
--file-type
likewise, except do not append '*'
--format=WORD
across -x, commas -m, horizontal -x, long -l, single-column -1, verbose -l, vertical -C
--full-time
like -l --time-style=full-iso
-g like -l, but do not list owner
--group-directories-first
group directories before files; can be augmented with a --sort option, but any use of --sort=none (-U)
disables grouping
-G, --no-group
in a long listing, don't print group names
-h, --human-readable
with -l and -s, print sizes like 1K 234M 2G etc.
--si likewise, but use powers of 1000 not 1024
-H, --dereference-command-line
follow symbolic links listed on the command line
--dereference-command-line-symlink-to-dir
follow each command line symbolic link that points to a directory
--hide=PATTERN
do not list implied entries matching shell PATTERN (overridden by -a or -A)
--hyperlink[=WHEN]
hyperlink file names WHEN
--indicator-style=WORD
append indicator with style WORD to entry names: none (default), slash (-p), file-type (--file-type),
classify (-F)
-i, --inode
print the index number of each file
-I, --ignore=PATTERN
do not list implied entries matching shell PATTERN
-k, --kibibytes
default to 1024-byte blocks for file system usage; used only with -s and per directory totals
-l use a long listing format
-L, --dereference
when showing file information for a symbolic link, show information for the file the link references
rather than for the link itself
-m fill width with a comma separated list of entries
-n, --numeric-uid-gid
like -l, but list numeric user and group IDs
-N, --literal
print entry names without quoting
-o like -l, but do not list group information
-p, --indicator-style=slash
append / indicator to directories
-q, --hide-control-chars
print ? instead of nongraphic characters
--show-control-chars
show nongraphic characters as-is (the default, unless program is 'ls' and output is a terminal)
-Q, --quote-name
enclose entry names in double quotes
--quoting-style=WORD
use quoting style WORD for entry names: literal, locale, shell, shell-always, shell-escape, shell-es‐
cape-always, c, escape (overrides QUOTING_STYLE environment variable)
-r, --reverse
reverse order while sorting
-R, --recursive
list subdirectories recursively
-s, --size
print the allocated size of each file, in blocks
-S sort by file size, largest first
--sort=WORD
sort by WORD instead of name: none (-U), size (-S), time (-t), version (-v), extension (-X), width
--time=WORD
select which timestamp used to display or sort; access time (-u): atime, access, use; metadata change
time (-c): ctime, status; modified time (default): mtime, modification; birth time: birth, creation;
with -l, WORD determines which time to show; with --sort=time, sort by WORD (newest first)
--time-style=TIME_STYLE
time/date format with -l; see TIME_STYLE below
-t sort by time, newest first; see --time
-T, --tabsize=COLS
assume tab stops at each COLS instead of 8
-u with -lt: sort by, and show, access time; with -l: show access time and sort by name; otherwise: sort by
access time, newest first
-U do not sort; list entries in directory order
-v natural sort of (version) numbers within text
-w, --width=COLS
set output width to COLS. 0 means no limit
-x list entries by lines instead of by columns
-X sort alphabetically by entry extension
-Z, --context
print any security context of each file
--zero end each output line with NUL, not newline
-1 list one file per line
--help display this help and exit
--version
output version information and exit
The SIZE argument is an integer and optional unit (example: 10K is 10*1024). Units are K,M,G,T,P,E,Z,Y,R,Q
(powers of 1024) or KB,MB,... (powers of 1000). Binary prefixes can be used, too: KiB=K, MiB=M, and so on.
The TIME_STYLE argument can be full-iso, long-iso, iso, locale, or +FORMAT. FORMAT is interpreted like in
date(1). If FORMAT is FORMAT1<newline>FORMAT2, then FORMAT1 applies to non-recent files and FORMAT2 to recent
files. TIME_STYLE prefixed with 'posix-' takes effect only outside the POSIX locale. Also the TIME_STYLE envi‐
ronment variable sets the default style to use.
The WHEN argument defaults to 'always' and can also be 'auto' or 'never'.
Using color to distinguish file types is disabled both by default and with --color=never. With --color=auto, ls
emits color codes only when standard output is connected to a terminal. The LS_COLORS environment variable can
change the settings. Use the dircolors(1) command to set it.
Exit status:
0 if OK,
1 if minor problems (e.g., cannot access subdirectory),
2 if serious trouble (e.g., cannot access command-line argument). |
What does the command `readlink` do? | readlink - print resolved symbolic links or canonical file names |
How is the `readlink` used? | readlink [OPTION]... FILE... |
What is the detailed desciption of the `readlink`? | Note realpath(1) is the preferred command to use for canonicalization functionality.
Print value of a symbolic link or canonical file name
-f, --canonicalize
canonicalize by following every symlink in every component of the given name recursively; all but the
last component must exist
-e, --canonicalize-existing
canonicalize by following every symlink in every component of the given name recursively, all components
must exist
-m, --canonicalize-missing
canonicalize by following every symlink in every component of the given name recursively, without re‐
quirements on components existence
-n, --no-newline
do not output the trailing delimiter
-q, --quiet
-s, --silent
suppress most error messages (on by default)
-v, --verbose
report error messages
-z, --zero
end each output line with NUL, not newline
--help display this help and exit
--version
output version information and exit |
What does the command `chmod` do? | chmod - change file mode bits |
How is the `chmod` used? | chmod [OPTION]... MODE[,MODE]... FILE...
chmod [OPTION]... OCTAL-MODE FILE...
chmod [OPTION]... --reference=RFILE FILE... |
What is the detailed desciption of the `chmod`? | This manual page documents the GNU version of chmod. chmod changes the file mode
bits of each given file according to mode, which can be either a symbolic represen‐
tation of changes to make, or an octal number representing the bit pattern for the
new mode bits.
The format of a symbolic mode is [ugoa...][[-+=][perms...]...], where perms is ei‐
ther zero or more letters from the set rwxXst, or a single letter from the set ugo.
Multiple symbolic modes can be given, separated by commas.
A combination of the letters ugoa controls which users' access to the file will be
changed: the user who owns it (u), other users in the file's group (g), other users
not in the file's group (o), or all users (a). If none of these are given, the ef‐
fect is as if (a) were given, but bits that are set in the umask are not affected.
The operator + causes the selected file mode bits to be added to the existing file
mode bits of each file; - causes them to be removed; and = causes them to be added
and causes unmentioned bits to be removed except that a directory's unmentioned set
user and group ID bits are not affected.
The letters rwxXst select file mode bits for the affected users: read (r), write
(w), execute (or search for directories) (x), execute/search only if the file is a
directory or already has execute permission for some user (X), set user or group ID
on execution (s), restricted deletion flag or sticky bit (t). Instead of one or
more of these letters, you can specify exactly one of the letters ugo: the permis‐
sions granted to the user who owns the file (u), the permissions granted to other
users who are members of the file's group (g), and the permissions granted to users
that are in neither of the two preceding categories (o).
A numeric mode is from one to four octal digits (0-7), derived by adding up the bits
with values 4, 2, and 1. Omitted digits are assumed to be leading zeros. The first
digit selects the set user ID (4) and set group ID (2) and restricted deletion or
sticky (1) attributes. The second digit selects permissions for the user who owns
the file: read (4), write (2), and execute (1); the third selects permissions for
other users in the file's group, with the same values; and the fourth for other
users not in the file's group, with the same values.
chmod never changes the permissions of symbolic links; the chmod system call cannot
change their permissions. This is not a problem since the permissions of symbolic
links are never used. However, for each symbolic link listed on the command line,
chmod changes the permissions of the pointed-to file. In contrast, chmod ignores
symbolic links encountered during recursive directory traversals. |
What does the command `csplit` do? | csplit - split a file into sections determined by context lines |
How is the `csplit` used? | csplit [OPTION]... FILE PATTERN... |
What is the detailed desciption of the `csplit`? | Output pieces of FILE separated by PATTERN(s) to files 'xx00', 'xx01', ..., and output byte counts of each piece
to standard output.
Read standard input if FILE is -
Mandatory arguments to long options are mandatory for short options too.
-b, --suffix-format=FORMAT
use sprintf FORMAT instead of %02d
-f, --prefix=PREFIX
use PREFIX instead of 'xx'
-k, --keep-files
do not remove output files on errors
--suppress-matched
suppress the lines matching PATTERN
-n, --digits=DIGITS
use specified number of digits instead of 2
-s, --quiet, --silent
do not print counts of output file sizes
-z, --elide-empty-files
suppress empty output files
--help display this help and exit
--version
output version information and exit
Each PATTERN may be: |
What does the command `true` do? | true - do nothing, successfully |
How is the `true` used? | true [ignored command line arguments]
true OPTION |
What is the detailed desciption of the `true`? | Exit with a status code indicating success.
--help display this help and exit
--version
output version information and exit
NOTE: your shell may have its own version of true, which usually supersedes the version described here. Please
refer to your shell's documentation for details about the options it supports. |
What does the command `sort` do? | sort - sort lines of text files |
How is the `sort` used? | sort [OPTION]... [FILE]...
sort [OPTION]... --files0-from=F |
What is the detailed desciption of the `sort`? | Write sorted concatenation of all FILE(s) to standard output.
With no FILE, or when FILE is -, read standard input.
Mandatory arguments to long options are mandatory for short options too. Ordering options:
-b, --ignore-leading-blanks
ignore leading blanks
-d, --dictionary-order
consider only blanks and alphanumeric characters
-f, --ignore-case
fold lower case to upper case characters
-g, --general-numeric-sort
compare according to general numerical value
-i, --ignore-nonprinting
consider only printable characters
-M, --month-sort
compare (unknown) < 'JAN' < ... < 'DEC'
-h, --human-numeric-sort
compare human readable numbers (e.g., 2K 1G)
-n, --numeric-sort
compare according to string numerical value
-R, --random-sort
shuffle, but group identical keys. See shuf(1)
--random-source=FILE
get random bytes from FILE
-r, --reverse
reverse the result of comparisons
--sort=WORD
sort according to WORD: general-numeric -g, human-numeric -h, month -M, numeric -n, random -R, version -V
-V, --version-sort
natural sort of (version) numbers within text
Other options:
--batch-size=NMERGE
merge at most NMERGE inputs at once; for more use temp files
-c, --check, --check=diagnose-first
check for sorted input; do not sort
-C, --check=quiet, --check=silent
like -c, but do not report first bad line
--compress-program=PROG
compress temporaries with PROG; decompress them with PROG -d
--debug
annotate the part of the line used to sort, and warn about questionable usage to stderr
--files0-from=F
read input from the files specified by NUL-terminated names in file F; If F is - then read names from
standard input
-k, --key=KEYDEF
sort via a key; KEYDEF gives location and type
-m, --merge
merge already sorted files; do not sort
-o, --output=FILE
write result to FILE instead of standard output
-s, --stable
stabilize sort by disabling last-resort comparison
-S, --buffer-size=SIZE
use SIZE for main memory buffer
-t, --field-separator=SEP
use SEP instead of non-blank to blank transition
-T, --temporary-directory=DIR
use DIR for temporaries, not $TMPDIR or /tmp; multiple options specify multiple directories
--parallel=N
change the number of sorts run concurrently to N
-u, --unique
with -c, check for strict ordering; without -c, output only the first of an equal run
-z, --zero-terminated
line delimiter is NUL, not newline
--help display this help and exit
--version
output version information and exit
KEYDEF is F[.C][OPTS][,F[.C][OPTS]] for start and stop position, where F is a field number and C a character po‐
sition in the field; both are origin 1, and the stop position defaults to the line's end. If neither -t nor -b
is in effect, characters in a field are counted from the beginning of the preceding whitespace. OPTS is one or
more single-letter ordering options [bdfgiMhnRrV], which override global ordering options for that key. If no
key is given, use the entire line as the key. Use --debug to diagnose incorrect key usage.
SIZE may be followed by the following multiplicative suffixes: % 1% of memory, b 1, K 1024 (default), and so on
for M, G, T, P, E, Z, Y, R, Q.
*** WARNING *** The locale specified by the environment affects sort order. Set LC_ALL=C to get the traditional
sort order that uses native byte values. |
What does the command `ln` do? | ln - make links between files |
How is the `ln` used? | ln [OPTION]... [-T] TARGET LINK_NAME
ln [OPTION]... TARGET
ln [OPTION]... TARGET... DIRECTORY
ln [OPTION]... -t DIRECTORY TARGET... |
What is the detailed desciption of the `ln`? | In the 1st form, create a link to TARGET with the name LINK_NAME. In the 2nd form, create a link to TARGET in
the current directory. In the 3rd and 4th forms, create links to each TARGET in DIRECTORY. Create hard links
by default, symbolic links with --symbolic. By default, each destination (name of new link) should not already
exist. When creating hard links, each TARGET must exist. Symbolic links can hold arbitrary text; if later re‐
solved, a relative link is interpreted in relation to its parent directory.
Mandatory arguments to long options are mandatory for short options too.
--backup[=CONTROL]
make a backup of each existing destination file
-b like --backup but does not accept an argument
-d, -F, --directory
allow the superuser to attempt to hard link directories (note: will probably fail due to system restric‐
tions, even for the superuser)
-f, --force
remove existing destination files
-i, --interactive
prompt whether to remove destinations
-L, --logical
dereference TARGETs that are symbolic links
-n, --no-dereference
treat LINK_NAME as a normal file if it is a symbolic link to a directory
-P, --physical
make hard links directly to symbolic links
-r, --relative
with -s, create links relative to link location
-s, --symbolic
make symbolic links instead of hard links
-S, --suffix=SUFFIX
override the usual backup suffix
-t, --target-directory=DIRECTORY
specify the DIRECTORY in which to create the links
-T, --no-target-directory
treat LINK_NAME as a normal file always
-v, --verbose
print name of each linked file
--help display this help and exit
--version
output version information and exit
The backup suffix is '~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX. The version control method may be
selected via the --backup option or through the VERSION_CONTROL environment variable. Here are the values:
none, off
never make backups (even if --backup is given)
numbered, t
make numbered backups
existing, nil
numbered if numbered backups exist, simple otherwise
simple, never
always make simple backups
Using -s ignores -L and -P. Otherwise, the last option specified controls behavior when a TARGET is a symbolic
link, defaulting to -P. |
What does the command `tty` do? | tty - print the file name of the terminal connected to standard input |
How is the `tty` used? | tty [OPTION]... |
What is the detailed desciption of the `tty`? | Print the file name of the terminal connected to standard input.
-s, --silent, --quiet
print nothing, only return an exit status
--help display this help and exit
--version
output version information and exit |
What does the command `rm` do? | rm - remove files or directories |
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