vi | visudo | vmstat

vi, vim

vi is an old Unix text editor. Nowdays, it is usually just an alias for vim (vi improved), that is upwards compatible with vi. Online help is available through :help command.

vi [options] [files]

If filename is missing, ~ starts with an empty buffer. You can also use view (starts ~ in read only mode), gvim, gview (GUI versions), rvim, rview, rgvim, rgview (modes with restrictions: no shell cmds, no suspend). Besides old vi cmds, vim accepts many std key combinations available with other editors (like MS Notepad).

Some options

--help    --version

-V verbose;
+[n] position cursor on line n (or last line, if n is missing);

+/pattern

position cursor on the first occurrence of pattern;

-b binary mode; allows to edit binary or executable files;
-C force compatibility with vi;
-d start in diff mode (2 or 3 files must be specified);
-e start in ex mode (ancient Unix editor);
-h help (cmd line args and options);
-m disable file modification;
-n do not use a swap file (useful when file is on a very slow media); recovery after crash will be impossible;

-o[n]

open n windows stacked; if n is missing, open one window for each file;

-O[n]

open n windows side by side; if n is missing, open one window for each file;

-R read-only mode; can be reset with :set noro;
-r list swap files and info about using them for recovery;

-r file

recovery mode; use swap file to recover a crashed editing session; swap file has the same name as the text file with extension .swp appended;

-x use encryption when writing files (you'll be prompted for a crypt key);
General commands
ESC switch to the command mode;
Cursor control

← / → / ↓ / ↑

move cursor left, right, down, up (h / l / j / k);

w / e

to the beginning / end of the next word;

b to the beginning of the prev word;

Home / End

to the beginning / end of line (^ / $);

G to the EOF;
1G to the BOF;
nG to the line number n;

H / M / L

to the top / middle / bottom line;

CTRL + G

output current line number;

CTRL + F

page down;

CTRL + B

page up;

CTRL + D

half-screen down;

CTRL + U

half-screen up;

Add, Insert (command mode)
a add text;
i insert text;
o insert an empty line below current position;
Delete (command mode)
x delete char;
dw delete from curr pos to the end of word;
dd delete current line;
D delete from curr pos to the EOL;
nx delete n characters;
ndd delete n lines;
ndw delete n words;
dG delete from curr pos to the EOF;
d1G delete from curr pos to the BOF;
u undo;
U undo all changes in this line;
:e! restart editing from last save;
Copy, Paste (command mode)
yy copy line to the nameless buffer;
nyy copy n lines to the nameless buffer;
yw copy word to the nameless buffer;
nyw copy n words to the nameless buffer;

"ayy

copy line to the buffer "a";

"byw

copy word to the buffer "b";

"Byw

add word to the contents of the buffer "b";

p paste from the nameless buffer;
"ap paste from the buffer "a";

"add

delete line to the buffer "a";

dw delete word to the nameless buffer;
Find, Search, Replace (command mode)
fc find next c char;
Fc find prev c char;
";" repeat last search;
"," reverse last search;

/str

find next str;

?str

find previous str;

n repeat last '/' or '?' cmd;
N reverse last '/' or '?' cmd;

:start,finish s/find/replace/g

general cmd syntax;

:1,$s/the/The/g

replace the with The (global, all file);

:%s/the/The/g %

like previous;

:.,5s/^.*//g

remove all from curr pos to the 5th line;

:%s/the/The/gc

replace the with The, ask for acknowledgement;

:%s/^....//g

remove first 4 characters (global);

:1,5s/help/&ing/g

replace help with helping in first 5 lines;

:%s/ */&&/g

double number of spaces between words;

Exit / Save commands
:w write (save);

:w file

write to file;

:r file

read file;

:q quit;
ZZ same as :wq (write and quit);

visudo

edits the sudoers file (default is /etc/sudoers) in a safe fashion.

visudo [options]

The file is locked at the start and checked at the exit. If a syntax error is found, user gets a warning message and the following alternatives:

The last option is dangerous and should not be used in normal situations!

There is a hard-coded list of editors to be used (set at the compile time). Env vars VISUAL, EDITOR are ignored unless they set an editor from that list.

Options

-h    --help    -V    --vesrion

-c enable check-only mode (the existing sudoers file will be checked for syntax and a message detailing its status will be sent to stdout);
-f specify an alternate sudoers file location; with this option ~ will edit (or check) the file of your choice, instead of /etc/sudoers;
-q quiet mode (details about syntax errors are not printed);
-s enable strict checking of the sudoers file;

vmstat

reports info about processes, memory, paging, block I/O, traps and CPU activity. The first report gives averages since the last reboot, additional reports give info on a sampling period. The proc and memory reports are instantaneous in either case. ~ does not count itself.

vmstat [options] [period [count]]

period is an interval between updates (in seconds), count is the number of updates (infinity by default).

vmstat 3 5

show 5 updates [of system performance info] with an interval of 3s;

vmstat -S K 5 10

show 10 updates [of system performance info] with an interval of 5s, show sizes in kilobytes;

vmstat -d

show disk statistics (cumulative);

vmstat -s

show event counters and memory stats;

Options

-h    --help    -V    --vesrion

-a display active/inactive memory;
-f display the number of forks since boot;
-m display slabinfo;
-n display the header only once;
-s display a table of various event counters and memory stats;
-d report disk stats;

-p part

report detailed stats for the specified disk partition;

-S k|K|m|M

show sizes in bytes*n, where n is 1000 (k) or 1024 (K) or 1000000 (m) or 1048576 (M);

Field description

Processes

r the number of processes waiting for run time;
b the number of processes in uninterruptible sleep;

Memory

swpd the amount of virtual memory used;
free the amount of idle memory;
buff the amount of memory used as buffers;
cache the amount of memory used as cache;
inact the amount of inactive memory (-a);
active  the amount of active memory (-a);

Swap

si the amount of memory swapped in from disk (per sec);
so the amount of memory swapped out (per sec);

IO

bi blocks received from a block device (per sec);
bo blocks sent to a block device (per sec);

System

in the num of interrupts per sec, including clock;
cs the number of context switches per sec;

CPU

us time spent running non-kernel code;
sy time spent running kernel code;
id time spent idle;
wa time spent waiting for IO;
Field description for disk mode

Reads

total total reads completed successfully;
merged grouped reads (resulting in one I/O);
sectors  sectors read successfully;
ms milliseconds spent reading;

Writes

total total writes completed successfully;
merged grouped writes (resulting in one I/O);
sectors  sectors written successfully;
ms milliseconds spent writing;

IO

cur I/O in progress;
s seconds spent for I/O;
Field description for disk partition mode
reads total num of reads issued to this partition;
read sectors total read sectors for partition;
writes total num of writes issued to this partition;
requested writes  total num of write requests made for partition;
Field description for slab mode
cache cache name;
num num of currently active objects;
total total num of available objects;
size size of each object;
pages num of pages with at least one active object;
totpages  total num of allocated pages;
pslab num of pages per slab;