Linux Commands

dd

Convert and copy a file.

dd returns current copy status when sent an HUP signal. Type in another shell:

while :; sleep 5; do killall -s SIGHUP1 dd; done

This will force dd to update its status every 5sec.

dpkg

Package manager for Debian / Ubuntu. See Package Management#Ubuntu / Debian

find

find . -exec echo '{}' \;                                #semi-colon must be escaped!
find . -exec echo one '{}' \; -exec echo two '{}' \;     #to execute several commands on one match

grep

grep -Rsl PATTERN [FILE]            # Recursive, no error output, only list filename
grep BASIC-REG-EXP-PATTERN [FILE]   # Use classic regexp (like "dma\|DMA")
egrep EXT-REG-EXP-PATTERN [FILE]    # Same as grep -E. Use extended regexp (like "dma|DMA")
fgrep FIXED-STRINGS-REG-EXP [FILE]  # Same as grep -F. Pattern is a list of strings to match.
grep -n PATTERN [FILE]              # Print matched line numbers.
grep -- "-s" [FILE]                 # Search for text "-s"
grep -e "-s" [FILE]                 # Search for text "-s" - alternative solution
grep -R -include=*.in PATTERN *     # Search recursively through folders, limiting to files matching pattern "*.in"
grep -R PATTERN *.in                # Idem, but matching pattern "*.in" also applies to folders.

netcat

TCP-IP swiss army knife (equivalent of the telnet program. Check wikipedia:netcat. Also known as command nc).

netstat

Print network connections, routing tables, interface statistics, masqurade connections, and multicast memberships

netstat -atpn      #All, tcp, socket program PID, numeric
netstat -rn        #Kernel route table, numberic

When listing sockets (default output), you'll get an output like:

% netstat -at Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 *:time *:* LISTEN tcp 0 0 localhost:mysql *:* LISTEN tcp 0 0 andLinux.local:43449 windows-host:x11 ESTABLISHED

% netstat -atn Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:37 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN tcp 0 0 192.168.11.150:43449 192.168.11.1:6000 ESTABLISHED

Local Address

* or 0.0.0.0 means that the process accepts connection from any interface.

127.0.0.1 means it only accepts connection on localhost loopback (and so only connection that originates from local PC as well).

Any other IP address means that the process listen on the given port at the given IP address

recode

recode /cl../cr <dos.txt >mac.txt
recode /cr.. <mac.txt >unix.txt
recode ../cl <unix.txt >dos.txt
recode charset1/surface1..charset2/surface2 <input.txt >output.txt
recode /QP.. <qp.txt >normal.txt                                    # To convert quoted-printable text

charset		surface
us	ASCII (7 bits)	/cr	Carriage return as end of line (Mac text)
l1	ISO Latin-1 (ISO-8859-1, Western Europe, 8 bits)	/cl	Carriage return line feed as end of line (DOS text)
EUCJP	EUC-JP for Japanese (Unix)	/	Line feed as end of line (Unix text)
SJIS	Shift-JIS for Japanese (Microsoft)	/d1	Human readable bytewise decimal dump
ISO2022JP	Mail encoding for Japanese (7 bits)	/x1	Human readable bytewise hexidecimal dump
u2	UCS-2 (Universal Character Set, 2 bytes)	/64	Base64 encoded text
u8	UTF-8 (Universal Transformation Format, 8 bits)	/QP	Quoted-Printable encoded text

rpm

See Package Management#RPM's

sed

sed [OPTION]... {script-only-if-no-other-script} [input-file]...
sed -n                              # Silent - suppress automatic printing of pattern space
sed -r                              # Use extended regular expression
sed -i "s/foo/bar/" *.txt           # In-place file modification

References

• The SED Homepage on SourceForge
• The SED FAQ
• The SED man page
• Sed, a stream editor
• The sed one-liners

Regular expressions

The information below is only illustrative. See e.g. Wikipedia page for reference information. The list below is actually for extended regular expressions, which can be obtained in sed using option -r (sed -r).

Regexp	Description
.	Match any character
gray|grey	Match gray or grey
gr(a|e)y	Match gray or grey
gr[ae]y	Match gray or grey
file[^0-2]	Match file3 or file4, but not file0, file1, file2.
colou?r	(zero or one) - Match Color or Colour.
ab*c	(zero or more) - Match ac, abc, abbc, ....
ab+c	(one or more) - Match abc, abbc, abbbc, ....
a{3,5}	(at least m and not more than n times) - Match aaa, aaaa, aaaaa.
^on single line$	(start and end of line) - Match on single line on a single line.

When using standard (non-extended) regular expression, some special meta-characters (like the parenthesis ( ), or braces { }) must be quoted with backslash \.

socat

Command-line utility that establishes two bidirectional byte streams and transfers data between them ([1]). socat is the more powerful version of netcat.

socat -ly 'TCP4-LISTEN:143,reuseaddr,fork' PROXY:ton.imap.server:143|TCP:134.27.168.36:8080
ProxyCommand socat - 'PROXY:%h:%p,proxyauth=user:pass|SSL,verify=0|PROXY:my.server:443,proxyauth=user:pass|TCP:big.brother.proxy:8080'     #Using v2.0.0 beta

socat can be easily used as a replacement of telnet:

socat tcp:<host>:<port> -       #<port> can be a port number or service name (telnet,imap...)

Miscellaneous

htop

an improved top command (http://htop.sourceforge.net/index.php)

iconv

locale encoding conversions

konwert

fancy encoding conversions

mimencode

binary file conversion for the mail.;mkfifo

make FIFOs (named pipes)

pv, pipeview, pipebench

monitor the progress of data through a pipe

reformime

MIME E-mail reformatting tool

stat

display file or file system status

strace

trace system calls and signals

tee

read from standard input and write to standard output and files

tree

List the contents of directories in a tree-like format.

uuencode, uudecode

binary file conversion for Unix.

watch

Execute a program periodically, showing output full screen