Linux Command Line Tips

Joelhy

This is a list of linux commands for common operations.
Note items marked with • are valid/safe to paste without modification into a terminal, so
you may want to keep a terminal window open while reading this so you can
cut & paste
.
Command
Description
•
apropos word
Show commands pertinent to word. See also
threadsafe

which command
Show full path name of command

time command
See how long a command takes
•
time cat
Start stopwatch. Ctrl-d to stop. See also
sw
•
nice
info
Run a low priority command (info in this case)
•
renice 19 -p $$
Make shell (script) low priority. Use for non interactive tasks
•
look prefix
Quickly search (sorted) dictionary
•
grep
--color
expr...ion /usr/share/dict/words
Highlight occurances of regular expression in dictionary

gpg -c file
Encrypt file

gpg file.gpg
Decrypt file
•
alias hd='od -Ax -tx1z -v'
Handy hexdump. (usage e.g.: • hd /proc/self/cmdline | less)
•
alias realpath='readlink -f'
Canonicalize path. (usage e.g.: • realpath ~/../$USER)
•
set | grep $USER
Search current
environment
•
ls /usr/bin | pr -T9 -W$COLUMNS
Print in 9 columns to width of terminal

touch -c -t 0304050607 file
Set file timestamp (YYMMDDhhmm)
dir navigation
•
cd -
Go to previous directory
•
cd
Go to home directory

(cd dir && command)
Go to dir, execute command and return to current dir
•
pushd .
Put current dir on stack so you can popd back to it
CDs

gzip  cdrom.iso.gz
Save copy of data cdrom

mkisofs -V NAME -r dir | gzip > cdrom.iso.gz
Create cdrom image from contents of dir

mount -o loop cdrom.iso /mnt/dir
Mount the cdrom image at /mnt/dir (read only)

cdrecord -v dev=/dev/cdrom blank=fast
Clear a CDRW

gzip -dc cdrom.iso.gz | cdrecord -v dev=/dev/cdrom -
Burn cdrom image (use dev=ATAPI -scanbus to confirm dev)

cdparanoia -B
Rip audio tracks from CD to wav files in current dir

cdrecord -v dev=/dev/cdrom -audio *.wav
Make audio CD from all wavs in current dir (see also cdrdao)

oggenc --tracknum='track' track.cdda.wav -o 'track.ogg'
Make ogg file from wav file
archives

tar c dir/ | bzip2 > dir.tar.bz2
Make archive of dir/

bzip2 -dc dir.tar.bz2 | tar x
Extract archive (use gzip instead of bzip2 for tar.gz files)

tar c dir/ | gzip | gpg -c | ssh user@remote 'dd of=dir.tar.gz.gpg'
Make encrypted archive of dir/ on remote machine

find dir/ -name '*.txt' | tar c --files-from=- | bzip2 > dir_txt.tar.bz2
Make archive of subset of dir/ and below

find dir/ -name '*.txt' | xargs cp -a --target-directory=dir_txt/ --parents
Make copy of subset of dir/ and below

( tar c /dir/to/copy ) | ( cd /where/to/ && tar x -p )
Copy (with permissions) copy/ dir to /where/to/ dir

( cd /dir/to/copy && tar c . ) | ( cd /where/to/ && tar x -p )
Copy (with permissions) contents of copy/ dir to /where/to/

( tar c /dir/to/copy ) | ssh -C user@remote 'cd /where/to/ && tar x -p'
Copy (with permissions) copy/ dir to remote:/where/to/ dir

dd bs=1M if=/dev/hda | gzip | ssh user@remote 'dd of=hda.gz'
Backup harddisk to remote machine
rsync (Use the --dry-run option for testing)

rsync -P rsync://rsync.server.com/path/to/file file
Only get diffs. Do multiple times for troublesome downloads

rsync --bwlimit=1000 fromfile tofile
Locally copy with rate limit. It's like nice for I/O

rsync -az -e ssh --delete ~/public_html/ remote.com:'~/public_html'
Mirror web site (using compression and encryption)

rsync -auz -e ssh remote:/dir/ . && rsync -auz -e ssh . remote:/dir/
Synchronize current directory with remote one
file searching
•
alias l='ls -l --color=auto'
quick dir listing
•
ls -lrt
List files by date. See also
newest

find -name '*.[ch]' | xargs grep -E 'expr'
Search 'expr' in this dir and below. See also
findrepo

find -type f -print0 | xargs -r0 grep -F 'string'
Search all regular files for 'string' in this dir and below

find -maxdepth 1 -type f | xargs grep -F 'string'
Search all regular files for 'string' in this dir

find -maxdepth 1 -type d | while
read
dir; do echo $dir; echo cmd2; done
Process each item with multiple commands (in while loop)
•
find -type f ! -perm -444
Find files not readable by all (useful for web site)
•
find -type d ! -perm -111
Find dirs not accessible by all (useful for web site)
•
locate -r 'file[^/]*\.txt'
Search cached index for names. This re is like glob *file*.txt
networking (Note ifconfig, route, mii-tool, nslookup commands are obsolete)
•
ip link show
List interfaces

ethtool interface
List interface status

ip link set dev eth0 name wan
Rename eth0 to wan

ip addr add 1.2.3.4/24 brd + dev eth0
Add ip and mask(255.255.255.0)

ip link set dev interface up
Bring interface up (or down)

ip route add default via 1.2.3.254
Set default gateway to 1.2.3.254
•
tc qdisc add dev lo root handle 1:0 netem delay 20msec
Add 20ms latency to loopback device (for testing)
•
tc qdisc del dev lo root
Remove latency added above
•
host pixelbeat.org
Lookup ip address for name or vice versa
•
hostname -i
Lookup local ip address (equivalent to host `hostname`)
•
netstat -tupl
List internet services on a system
•
netstat -tup
List active connections to/from system
wget (multi purpose download tool)
•
(cd cmdline && wget -nd -pHEKk http://www.pixelbeat.org/cmdline.html)
Store local browsable version of a page to the current dir

wget -c http://www.example.com/large.file
Continue downloading a partially downloaded file

wget -r -nd -np -l1 -A '*.jpg' http://www.example.com/
Download a set of files to the current directory

wget ftp://remote/file[1-9].iso/
FTP supports globbing directly
•
wget -q -O- http://www.pixelbeat.org/timeline.html | grep 'a href' | head
Process output directly

echo 'wget url' | at 01:00
Download url at 1AM to current dir

wget --limit-rate=20k url
Do a low priority download (limit to 20
KB/s
in this case)

wget -nv --spider --force-html -i bookmarks.html
Check links in a file

wget --mirror http://www.example.com/
Efficiently update a local copy of a site (handy from cron)
windows (note samba is the package that provides all this windows specific networking support)
•
smbtree
Find windows machines. See also findsmb

nmblookup -A 1.2.3.4
Find the windows (netbios) name associated with ip address

smbclient -L windows_box
List shares on windows machine or samba server

mount -t smbfs -o fmask=666,guest //windows_box/share /mnt/share
Mount a windows share

echo 'message' | smbclient -M windows_box
Send popup to windows machine (off by default in XP sp2)
math
•
echo '(1 + sqrt(5))/2' | bc -l
Quick math (Calculate φ)
•
echo 'obase=16; ibase=10; 123' | bc
Base conversion (decimal to hexadecimal)
•
echo $((0x2dec))
Base conversion (hex to dec) ((shell arithmetic expansion))
•
echo 'pad=20; min=64; (100*10^6)/((pad+min)*8)' | bc
More complex (int) e.g. This shows max FastE packet rate
•
echo 'pad=20; min=64; print (100E6)/((pad+min)*8)' | python
Python handles scientific notation
•
echo 'pad=20; plot [64:1518] (100*10**6)/((pad+x)*8)' | gnuplot -persist
Plot FastE packet rate vs packet size
•
seq 100 | (tr '\n' +; echo 0) | bc
Add a column of numbers. See also
add
and
funcpy
text manipulation (note sed uses stdin and stdout, so if you want to edit files, append newfile)

sed 's/string1/string2/g'
Replace string1 with string2

sed 's/\(.*\)1/\12/g'
Modify anystring1 to anystring2

sed '/ *#/d; /^ *$/d'
Remove comments and blank lines

sed ':a; /\\$/N; s/\\\n//; ta'
Concatenate lines with trailing \

sed 's/[ \t]*$//'
Remove trailing spaces from lines

sed 's/\([\\`\\"$\\\\]\)/\\\1/g'
Escape shell metacharacters active within double quotes

sed -n '1000p;1000q'
Print 1000th line

sed -n '10,20p;20q'
Print lines 10 to 20

sed -n 's/.*\(.*\).*/\1/p;T;q'
Extract title from HTML web page

sort -t. -k1,1n -k2,2n -k3,3n -k4,4n
Sort IPV4 ip addresses
•
echo 'Test' | tr '[:lower:]' '[:upper:]'
Case conversion
•
tr -dc '[:print:]'
Filter non printable characters
•
grep 'processor' /proc/cpuinfo | wc -l
Count lines
set operations (Note
LANG=C
is for speed) (Note also these assume no duplicate lines within a file)

LANG=C sort file1 file2 | uniq
Union of unsorted files

LANG=C sort file1 file2 | uniq -d
Intersection of unsorted files

LANG=C sort file1 file1 file2 | uniq -u
Difference of unsorted files

LANG=C sort file1 file2 | uniq -u
Symmetric Difference of unsorted files

LANG=C comm file1 file2 | sed 's/^\t*//'
Union of sorted files

LANG=C comm -12 file1 file2
Intersection of sorted files

LANG=C comm -13 file1 file2
Difference of sorted files

LANG=C comm -3 file1 file2 | sed 's/^\t*//'
Symmetric Difference of sorted files
calendar
•
cal -3
Display a calendar
•
cal 9 1752
Display a calendar for a particular month year
•
date -d fri
What date is it this friday. See also
day
•
date --date='25 Dec' +%A
What day does xmas fall on, this year
•
date --date '1970-01-01 UTC 1234567890 seconds'
Convert number of seconds since the epoch to a date
•
TZ=':America/Los_Angeles' date
What time is it on West coast of US (use tzselect to find TZ)

echo "mail -s 'get the train' P@draigBrady.com
Email reminder
•
echo "DISPLAY=$DISPLAY xmessage cooker" | at "NOW + 30 minutes"
Popup reminder
locales
•
printf "%'d\n" 1234
Print number with thousands grouping appropriate to locale
•
echo "I live in `locale territory`"
Extract info from locale database
•
locale | cut -d= -f1 | xargs locale -kc | less
List fields in locale database
•
LANG=en_IE.utf8 locale int_prefix
Lookup locale info for specific country. See also
ccodes
disk space (See also
FSlint
)
•
ls -lSr
Show files, biggest last
•
du -s * | sort -k1,1rn | head
Show top disk users in current dir. See also
dutop
•
df -h
Show free disk space
•
df -i
Show free inodes
•
fdisk -l
Show disks partitions sizes and types (run as root)
•
rpm
-q -a --qf '%10{SIZE}\t%{NAME}\n' | sort -k1,1n
List all
packages
by installed size (Bytes) on rpm distros
•
dpkg
-query -W -f='${Installed-Size;10}\t${Package}\n' | sort -k1,1n
List all
packages
by installed size (KBytes) on deb distros
•
dd bs=1 seek=2TB if=/dev/null of=ext3.test
Create a large test file (taking no space). See also
truncate
monitoring/debugging
•
strace -c ls >/dev/null
Summarise/profile system calls made by command
•
strace -f -e open ls >/dev/null
List system calls made by command
•
ltrace -f -e getenv ls >/dev/null
List library calls made by command
•
lsof -p $$
List paths that process id has open
•
lsof ~
List processes that have specified path open
•
tcpdump not port 22
Show network traffic except ssh. See also
tcpdump_not_me
•
ps -e -o pid,args --forest
List processes in a hierarchy
•
ps -e -o pcpu,cpu,nice,state,cputime,args --sort pcpu | sed '/^ 0.0 /d'
List processes by % cpu usage
•
ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS
List processes by mem usage. See also
ps_mem.py
•
ps -C firefox-bin -L -o pid,tid,pcpu,state
List all threads for a particular process
•
ps -p 1,2
List info for particular process IDs
•
last reboot
Show system reboot history.
•
free -m
Show amount of (remaining) RAM (-m displays in MB)
•
watch -n1 'cat /proc/interrupts'
Watch changeable data continuously
System information (see also
sysinfo
)

hdparm -i /dev/hda
Show info about disk hda

hdparm -tT /dev/hda
Do a read speed test on disk hda

badblocks -s /dev/hda
Test for unreadable blocks on disk hda
•
mount | column -t
Show mounted filesystems on the system (and align output)
•
cat /proc/partitions
Show all partitions registered on the system
•
grep MemTotal /proc/meminfo
Show RAM total seen by the system
•
grep "model name" /proc/cpuinfo
Show CPU(s) info
•
lspci -tv
Show PCI info
•
lsusb -tv
Show USB info
recode (Obsoletes iconv, dos2unix, unix2dos)
•
recode -l | less
Show available conversions (aliases on each line)

recode windows-1252.. file_to_change.txt
Windows "ansi" to local charset (auto does CRLF conversion)

recode utf-8/CRLF.. file_to_change.txt
Windows utf8 to local charset

recode iso-8859-15..utf8 file_to_change.txt
Latin9 (western europe) to utf8

recode ../b64  file.b64
Base64 encode

recode /qp..  file.qp
Quoted printable decode

recode ..HTML  file.html
Text to HTML
•
recode -lf windows-1252 | grep euro
Lookup
table of characters
•
echo -n 0x80 | recode latin-9/x1..dump
Show what a code represents in latin-9 charmap
•
echo -n 0x20AC | recode ucs-2/x2..latin-9/x
Show latin-9 encoding
•
echo -n 0x20AC | recode ucs-2/x2..utf-8/x
Show utf-8 encoding
interactive
•
mc
Powerful filemanager that can browse rpm, tar, ftp, ssh, ...
•
screen
Virtual terminals with detach capability, ...
•
links
Web browser
•
gnuplot
Interactive/scriptable graphing
•
octave
Matlab like environment
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