原文章地址：The Linux man-pages project
Linux User’s Manual(1) - user commands
NAME
intro - introduction
to user commands
DESCRIPTION
Section
1 of the manual describes user commands
and tools,
for
example,
file manipulation tools, shells, compilers, web browsers,
file and image viewers
and editors,
and so
on.
NOTES
Linux
is a flavor
of UNIX,
and as a
first approximation all user
commands under UNIX work precisely
the same under Linux (
and FreeBSD
and lots
of other UNIX-like systems).
Under Linux, there are GUIs (graphical user interfaces),
where you
can point
and click
and drag,
and hopefully
get work done
without
first reading lots
of documentation. The traditional UNIX
environment
is a CLI (command line interface),
where you type
commands
to tell the computer what
to do. That
is faster
and more
powerful,
but requires finding out what
the commands are. Below a
bare minimum,
to get started.
Login
In order
to start working, you probably
first have
to open a session
by giving your username
and password. The program login(
1) now
starts a shell (command interpreter)
for you. In case
of a graphical
login, you
get a screen
with menus
or icons
and a mouse click will
start a shell
in a window. See also xterm(
1).
The shell
One types commands
to the shell,
the command interpreter. It
is not
built-
in,
but is just a program
and you can change your shell.
Everybody has her own favorite one. The standard one
is called sh.
See also ash(
1), bash(
1), chsh(
1), csh(
1), dash(
1), ksh(
1), zsh(
1).
A session might go like:
knuth login: aeb
Password: ********
$
date
Tue Aug
6 23:
50:
44 CEST
2002
$ cal
August
2002
Su Mo Tu We Th Fr Sa
1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31
$ ls
bin tel
$ ls -l
total
2
drwxrwxr-x
2 aeb
1024 Aug
6 23:
51 bin
-rw-rw-r
$ cat tel
maja
0501-
1136285
peter
0136-
7399214
$ cp tel tel2
$ ls -l
total
3
drwxr-xr-x
2 aeb
1024 Aug
6 23:
51 bin
-rw-r
-rw-r
$ mv tel tel1
$ ls -l
total
3
drwxr-xr-x
2 aeb
1024 Aug
6 23:
51 bin
-rw-r
-rw-r
$ diff tel1 tel2
$ rm tel1
$ grep maja tel2
maja
0501-
1136285
$
Here typing Control-D ended
the session.
The $ here was
the command prompt—
it is the shell's way
of indicating
that it is ready
for the next command. The prompt can be customized
in lots
of ways,
and one might include stuff like username, machine
name, current directory,
time,
and so
on. An assignment PS1=
"What
next, master? " would change
the prompt
as indicated.
We see
that there are commands
date (
that gives
date and time),
and
cal (
that gives a calendar).
The command ls lists
the contents of the current directory—
it tells
you what files you have. With a -l option
it gives a long listing,
that includes
the owner
and size
and date of the file,
and the
permissions people have
for reading
and/
or changing
the file. For
example,
the file "tel" here
is 37 bytes long, owned
by aeb
and the
owner can
read and write it, others can only
read it. Owner
and
permissions can be changed
by the commands chown
and chmod.
The command cat will show
the contents of a
file. (The
name is from
"concatenate and print": all files
given as parameters are
concatenated
and sent
to "standard output" (see stdout(
3)), here
the
terminal screen.)
The command cp (
from "copy") will
copy a
file.
The command mv (
from "move"),
on the other hand, only renames
it.
The command diff lists
the differences
between two files. Here there
was no output because there were no differences.
The command rm (
from "remove") deletes
the file,
and be careful!
it
is gone. No wastepaper basket
or anything. Deleted means lost.
The command grep (
from "g/re/p") finds occurrences
of a
string in one
or more files. Here
it finds Maja's telephone
number.
Pathnames
and the current directory
Files live
in a large tree,
the file hierarchy. Each has a pathname
describing
the path
from the root
of the tree (which
is called /)
to
the file. For example, such a full pathname might be /home/aeb/tel.
Always using full pathnames would be inconvenient,
and the name of a
file in the current directory may be abbreviated
by giving only
the
last component. That
is why /home/aeb/tel can be abbreviated
to tel
when
the current directory
is /home/aeb.
The command pwd prints
the current directory.
The command cd changes
the current directory.
Try alternatively cd
and pwd commands
and explore cd usage:
"cd",
"cd
.",
"cd ..",
"cd /" and "cd ~".
Directories
The command mkdir makes a new directory.
The command rmdir removes a directory
if it is empty,
and complains
otherwise.
The command find (
with a rather baroque syntax) will find files
with
given name or other properties. For example,
"find . -name tel"
would find
the file tel starting
in the present directory (which
is
called .). And
"find / -name tel" would do
the same,
but starting
at
the root
of the tree. Large searches
on a multi-GB disk will be
time-consuming,
and it may be better
to use locate(
1).
Disks
and filesystems
The command mount will attach
the filesystem found
on some disk (
or
floppy,
or CDROM
or so)
to the big filesystem hierarchy. And umount
detaches
it again. The command df will
tell you how much
of your
disk
is still free.
Processes
On a UNIX system many user
and system processes
run simultaneously.
The one you are talking
to runs
in the foreground,
the others
in the
background. The command ps will show you which processes are active
and what numbers these processes have. The command kill allows you
to get rid
of them. Without option this
is a friendly request:
please go away. And
"kill -9" followed
by the number of the process
is an immediate kill. Foreground processes can often be killed
by
typing Control-C.
Getting information
There are thousands
of commands, each
with many options.
Traditionally commands are documented
on man pages, (like this one),
so
that the command
"man kill" will document
the use
of the command
"kill" (
and "man man" document
the command
"man"). The program man
sends
the text through some pager, usually less. Hit
the space bar
to get the next page, hit q
to quit.
In documentation
it is customary
to refer
to man pages
by giving
the
name and section
number,
as in man(
1). Man pages are terse,
and
allow you
to find quickly
some forgotten detail. For newcomers an
introductory
text with more examples
and explanations
is useful.
A lot
of GNU/FSF software
is provided
with info files. Type
"info
info" for an introduction
on the use
of the program info.
Special topics are often treated
in HOWTOs. Look
in
/usr/share/doc/howto/en
and use a browser
if you find HTML files
there.
SEE ALSO
ash(1),
bash(1),
chsh(1),
csh(1),
dash(1),
ksh(1),
locate(1),
login(1),
man(1),
xterm(1),
zsh(1),
wait(2),
stdout(3),
man-pages(7),
standards(7)
COLOPHON
This page is part
of release
4.11 of the Linux man-pages project. A
description
of the project, information about reporting bugs,
and the
latest
version of this page, can be found
at
https://www.kernel.org/doc/man-pages/.
Linux
2015-
07-
23 INTRO(
1)
Linux User’s Manual(2) - system calls
NAME
intro - introduction
to system calls
DESCRIPTION
Section
2 of the manual describes
the Linux system calls. A system
call
is an entry point
into the Linux kernel. Usually, system calls
are
not invoked directly: instead, most system calls have
corresponding C library wrapper functions which perform
the steps
required (e.g., trapping
to kernel mode)
in order
to invoke
the
system call. Thus, making a system call looks
the same
as invoking a
normal library function.
In many cases,
the C library wrapper function
does nothing more than:
* copying arguments
and the unique system call
number to the
registers
where the kernel expects them;
* trapping
to kernel mode,
at which point
the kernel
does the real
work
of the system call;
* setting errno
if the system call returns an
error number when
the
kernel returns
the CPU
to user mode.
However,
in a few cases, a wrapper function may do rather more than
this,
for example, performing
some preprocessing
of the arguments
before trapping
to kernel mode,
or postprocessing
of values returned
by the system call. Where this
is the case,
the manual pages
in
Section
2 generally
try to note
the details
of both
the (usually GNU)
C library API interface
and the raw system call. Most commonly,
the
main DESCRIPTION will focus
on the C library interface,
and
differences
for the system call are covered
in the NOTES section.
For a
list of the Linux system calls, see syscalls(
2).
RETURN VALUE
On error, most
system calls
return a negative error
number (i.e.,
the
negated
value of one of the constants described
in errno(
3)). The C
library wrapper hides this detail
from the caller: when
a system call
returns
a negative
value,
the wrapper copies
the absolute
value into
the errno
variable,
and returns -
1 as the return value of the
wrapper.
The
value returned
by a successful
system call depends
on the call.
Many
system calls
return 0 on success, but some can return nonzero
values
from a successful call. The details are described
in the
individual manual pages.
In some cases,
the programmer must define
a feature test macro
in
order
to obtain
the declaration
of a system call
from the header
file
specified
in the man page SYNOPSIS section. (Where required, these
feature test macros must be defined
before including
any header
files.) In such cases,
the required macro is described
in the man
page. For further information
on feature test macros, see
feature_test_macros(
7).
Certain terms
and abbreviations are used
to indicate UNIX variants
and standards
to which calls
in this section conform. See
standards(
7).
NOTES
Calling directly
In most cases,
it is unnecessary
to invoke
a system call directly,
but there are times when
the Standard C library does
not implement
a
nice wrapper
function for you. In this case, the programmer must
manually invoke
the system call
using syscall(
2). Historically, this
was also possible
using one of the _syscall macros described
in
_syscall(
2).
Authors
and copyright conditions
Look
at the header
of the manual page source
for the author(s)
and
copyright conditions. Note that these can be different
from page
to
page!
SEE ALSO
_
syscall(2),
syscall(2),
syscalls(2),
errno(3),
intro(3),
capabilities(7),
credentials(7),
feature_test_macros(7),
mq_overview(7),
path_resolution(7),
pipe(7),
pty(7),
sem_overview(7),
shm_overview(7),
signal(7),
socket(7),
standards(7),
svipc(7),
symlink(7),
time(7)
COLOPHON
This page is part
of release
4.11 of the Linux man-pages project. A
description
of the project, information about reporting bugs,
and the
latest
version of this page, can be found
at
https://www.kernel.org/doc/man-pages/.
Linux
2014-
02-
20 INTRO(
2)
Linux User’s Manual(3) - library functions
NAME
intro - introduction
to library functions
DESCRIPTION
Section
3 of the manual describes all library functions excluding
the
library functions (
system call wrappers) described
in Section
2,
which implement
system calls.
Many
of the functions described
in the section are part
of the
Standard C Library (libc). Some functions are part
of other
libraries (e.g.,
the math library, libm,
or the real-
time library,
librt)
in which
case the manual page will indicate
the linker option
needed
to link against
the required library (e.g., -lm
and -lrt,
respectively,
for the aforementioned libraries).
In some cases,
the programmer must define
a feature test macro
in
order
to obtain
the declaration
of a function from the header file
specified
in the man page SYNOPSIS section. (Where required, these
feature test macros must be defined
before including
any header
files.) In such cases,
the required macro is described
in the man
page. For further information
on feature test macros, see
feature_test_macros(
7).
Certain terms
and abbreviations are used
to indicate UNIX variants
and standards
to which calls
in this section conform. See
standards(
7).
NOTES
Authors
and copyright conditions
Look
at the header
of the manual page source
for the author(s)
and
copyright conditions. Note
that these can be different
from page
to
page!
SEE ALSO
intro(2),
errno(3),
capabilities(7),
credentials(7),
environ(7),
feature_test_macros(7),
libc(7),
math_error(7),
path_resolution(7),
pthreads(7),
signal(7),
standards(7)
COLOPHON
This page is part
of release
4.11 of the Linux man-pages project. A
description
of the project, information about reporting bugs,
and the
latest
version of this page, can be found
at
https://www.kernel.org/doc/man-pages/.
Linux
2010-
11-
11 INTRO(
3)
Linux User’s Manual(4) - special files
NAME
intro - introduction
to special
files
DESCRIPTION
Section
4 of the manual describes special
files (devices).
FILES
/dev/* — device files
NOTES
Authors
and copyright conditions
Look
at the header
of the manual page source
for the author(s)
and
copyright conditions. Note
that these can be different
from page
to
page!
SEE ALSO
standards(7)
COLOPHON
This page is part
of release
4.11 of the Linux man-pages project. A
description
of the project, information about reporting bugs,
and the
latest
version of this page, can be found
at
https://www.kernel.org/doc/man-pages/.
Linux
2007-
10-
23 INTRO(
4)
NAME
intro - introduction
to file formats
and filesystems
DESCRIPTION
Section
5 of the manual describes various
file formats,
as well
as
the corresponding C structures,
if any. In addition, there are
a
number of pages that document various filesystems.
NOTES
Authors
and copyright conditions
Look
at the header
of the manual page source
for the author(s)
and
copyright conditions. Note
that these can be different
from page
to
page!
SEE ALSO
standards(7)
COLOPHON
This page is part
of release
4.11 of the Linux man-pages project. A
description
of the project, information about reporting bugs,
and the
latest
version of this page, can be found
at
https://www.kernel.org/doc/man-pages/.
Linux
2017-
03-
13 INTRO(
5)
Linux User’s Manual(6) - games
NAME
intro - introduction
to games
DESCRIPTION
Section
6 of the manual describes all
the games
and funny little
programs available
on the system.
NOTES
Authors
and copyright conditions
Look
at the header
of the manual page source
for the author(s)
and
copyright conditions. Note
that these can be different
from page
to
page!
COLOPHON
This page is part
of release
4.11 of the Linux man-pages project. A
description
of the project, information about reporting bugs,
and the
latest
version of this page, can be found
at
https://www.kernel.org/doc/man-pages/.
Linux
2007-
10-
23 INTRO(
6)
Linux User’s Manual(7) - overview, conventions, and miscellany section
NAME
intro - introduction
to overview, conventions,
and miscellany section
DESCRIPTION
Section
7 of the manual provides overviews
on various topics,
and
describes conventions
and protocols,
character set standards,
the
standard filesystem layout,
and miscellaneous other things.
NOTES
Authors
and copyright conditions
Look
at the header
of the manual page source
for the author(s)
and
copyright conditions. Note
that these can be different
from page
to
page!
SEE ALSO
standards(7)
COLOPHON
This page is part
of release
4.11 of the Linux man-pages project. A
description
of the project, information about reporting bugs,
and the
latest
version of this page, can be found
at
https://www.kernel.org/doc/man-pages/.
Linux
2007-
10-
23 INTRO(
7)
Linux User’s Manual(8) - administration and privileged commands
NAME
intro - introduction
to administration
and privileged commands
DESCRIPTION
Section
8 of the manual describes commands which either can be
or are
used only
by the superuser, like
system-administration commands,
daemons,
and hardware-related commands.
As
with the commands described
in Section
1,
the commands described
in this section terminate
with an exit status that indicates whether
the command succeeded or failed. See intro(1) for more information.
NOTES
Authors
and copyright conditions
Look
at the header
of the manual page source
for the author(s)
and
copyright conditions. Note
that these can be different
from page
to
page!
COLOPHON
This page is part
of release
4.11 of the Linux man-pages project. A
description
of the project, information about reporting bugs,
and the
latest
version of this page, can be found
at
https://www.kernel.org/doc/man-pages/.
Linux
2007-
10-
23 INTRO(
8)
