Showing posts with label Linux commands. Show all posts
Showing posts with label Linux commands. Show all posts
Linux Commands For Beginners
TL;DR
- Basic Linux commands that we use literally all the time.
alias
alias grep=“grep –color” alias
ps
- print pid: ps -C {program-name} -o pid=
- Show full command: ps -f | less
- ps detects the size of your terminal window and clips to that.
xargs
- use \0 as the delimiter and -0 to use it
- printf ‘%s\0’ Hello Hola Bonjour | xargs -0 -I _ echo _ Landon
Search
Sort files by date then grep
- ls -rt *.log | xargs grep -l
List open files
- ls -l /proc/${pid}/fd
- Use this when lsof is not installed
- lsof -p ${pid}
watch
- watch -n 5 curl -s localhost:8983/show/health
- -d: highlights the changes
curl
pbcopy (take standard input to clipboard) + pbpaste (take data from clipboard to standard output)
diff
sed
- sed -n ‘16224,16482p’ filename > newfile
System
Check the age of the system
- rpm -qi basesystem | grep “Install Date”
Misc
- cd $(dirname ${file_full_path})
- tar xfz somefilename.tar.gz
- dirname, basename, realpath
- Copy one file to multiple file names
- cat 1.ods | tee {jan,feb,mar}-{Rep,graph}.ods >/dev/null
- tail -f **/*.log
Get current working directory of a process
- pwdx
- lsof -p
| grep cwd - readlink -e /proc/
/cwd ##### [View a range of bash history] - fl -l ${start} ${end}
- history | sed ‘start,{end}p’
- lsof -p
Brace expansion
- mkdir -p {f1, f2}
- for i in {1..3}; do echo $i; done
- {START..END..INCREMENT}
Command History
| !!:n | where n is the 0-based position of the argument you want |
| !$ | last argument from previous command |
| !^ | first argument (after the program/built-in/script) from previous command |
| !! | previous command (often pronounced “bang bang”) |
| !n | command number n from history |
| !pattern | most recent command matching pattern |
| !!:s/find/replace | last command, substitute find with replace |
| :p | print the command - !!:p, !!n:p |
Related Posts
Bash Scripting Essentials
Brace Expansion
chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
Special Variables
$? Exit value of last executed command.
pid=$!
wait $pid
$! Process number of last background command.
$0 First word; that is, the command name. This will have the full pathname if it was found via a PATH search.
$n Individual arguments on command line (positional parameters).
$# Number of command-line arguments.
“$*” All arguments on command line as one string (“$1 $2…”). The values are separated by the first character in $IFS.
“$@” All arguments on command line, individually quoted (“$1” “$2” …).
Tests
-n string is not null.
-z string is null, that is, has zero length
Testing for File Characteristics
-d File is a directory
-e File exists
-f File is a regular file
-s File has a size greater than zero
-r, -w, -x, -s - socket
[ -d "$dir" ] && echo "$dir exists." || echo "$dir doesn't exists."
Testing with Pattern Matches
== pattern
=~ ere
if [[ "${MYFILENAME}" == *.jpg ]]
-a, &&
-o, ||
if [ ! -d $param ]
if [ $? -ne 0 ]
Parsing
HEAP_DUMP_DIR=$(sed 's/-XX:HeapDumpPath=\([^ ]*\)/\1/' <<< $param)
Function
Use variable $1, $2..$n to access argument passed to the function.
Hello () {
echo "Hello $1 $2"
return 10
}
Return value in bash
echo in the function, capture the result in caller $()
Hello a b
for i in $( command ); do command $i; done
for i in $( command ); do
command $i
done
if [ "$var" == "value" ]; then
else
fi
Google Shell Style Guide
quote your variables; prefer "${var}" over "$var",
Use
while IFS=, read var1 var2 var3; do
Use Local Variables
chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
Special Variables
$? Exit value of last executed command.
pid=$!
wait $pid
$! Process number of last background command.
$0 First word; that is, the command name. This will have the full pathname if it was found via a PATH search.
$n Individual arguments on command line (positional parameters).
$# Number of command-line arguments.
“$*” All arguments on command line as one string (“$1 $2…”). The values are separated by the first character in $IFS.
“$@” All arguments on command line, individually quoted (“$1” “$2” …).
Tests
-n string is not null.
-z string is null, that is, has zero length
Testing for File Characteristics
-d File is a directory
-e File exists
-f File is a regular file
-s File has a size greater than zero
-r, -w, -x, -s - socket
[ -d "$dir" ] && echo "$dir exists." || echo "$dir doesn't exists."
Testing with Pattern Matches
if [[ "${MYFILENAME}" == *.jpg ]]
-a, &&
-o, ||
if [ ! -d $param ]
if [ $? -ne 0 ]
Parsing
HEAP_DUMP_DIR=$(sed 's/-XX:HeapDumpPath=\([^ ]*\)/\1/' <<< $param)
Function
Use variable $1, $2..$n to access argument passed to the function.
Hello () {
echo "Hello $1 $2"
return 10
}
Return value in bash
echo in the function, capture the result in caller $()
Hello a b
for i in $( command ); do command $i; done
for i in $( command ); do
command $i
done
if [ "$var" == "value" ]; then
else
fi
Google Shell Style Guide
quote your variables; prefer "${var}" over "$var",
Use
$(command) instead of backticks.[[ ... ]] is preferred over [, test- [[ ... ]] reduces errors as no pathname expansion or word splitting takes place between [[ and ]] and [[ ... ]] allows for regular expression matching where [ ... ] does not
Use readonly or declare -r to ensure they're read only.
Make variable readonly: readonly var=value
Make function readonly: readonly -f function
readonly -p/-f
if [[ -f ~/.bashrc ]]; then
source ~/.bashrc
fi
[ ! -f $FILE ] && { echo "$FILE not found"; exit -1; }
$(( $a+$b )) to execute arithmetic expressions
Put ; do and ; then on the same line as the while, for or if.
Prefer brace-quoting all other variables.
Use "$@" unless you have a specific reason to use $*.
- "$@" will retain arguments as-is, so no args provided will result in no args being passed on;
- "$*" expands to one argument, with all args joined by (usually) spaces, so no args provided will result in one empty string being passed on.
while IFS=, read var1 var2 var3; do
...
done < file.txt
local var="something"
local var
var="$(func)" || return
if [[ "${my_var}" = "some_string" ]]; then
do_something
fi
-z (string length is zero) and -n (string length is not zero)
if ! mv "${file_list}" "${dest_dir}/" ; then
fi
local var
var="$(func)" || return
if [[ "${my_var}" = "some_string" ]]; then
do_something
fi
-z (string length is zero) and -n (string length is not zero)
if ! mv "${file_list}" "${dest_dir}/" ; then
fi
Use set -o errexit (a.k.a. set -e) to make your script exit when a command fails.
Then add || true to commands that you allow to fail.
set -e - enable exit immediately
set +e - disable exit immediately
set -x - print a trace Use set -o nounset (a.k.a. set -u) to exit when your script tries to use undeclared variables.
Use set -o xtrace (a.k.a set -x) to trace what gets executed. Useful for debugging.
set -u Fail for undefined variable (set -o nounset)
Use $(( ... )), not expr for executing arithmetic expressions. which is more forgiving about space
set +e - disable exit immediately
set -x - print a trace Use set -o nounset (a.k.a. set -u) to exit when your script tries to use undeclared variables.
Use set -o xtrace (a.k.a set -x) to trace what gets executed. Useful for debugging.
set -u Fail for undefined variable (set -o nounset)
Use $(( ... )), not expr for executing arithmetic expressions. which is more forgiving about space
Use (( or let, not $(( when you don't need the result
Identify common problems with shellcheck.
Misc
while true; do some_commands_here; done
while true
do
some_commands_here
done
Run command until success
until $the_command; do echo "Try again"; done
while [ -n $(the command) ]; do echo "Try again";done;
Related
Essential Linux Commands for Developers
Misc
while true; do some_commands_here; done
while true
do
some_commands_here
done
Run command until success
until $the_command; do echo "Try again"; done
while [ -n $(the command) ]; do echo "Try again";done;
Related
Essential Linux Commands for Developers
Essential Linux Commands for Developers
Shortcuts:
Ctrl + a - Move to the start of line
Ctrl + e - Move to the end of line
Clear the screen: Ctrl + l
Search as you type. Ctrl + r and type the search term; Repeat Ctrl + r to loop through results.
!$
tac: print a file line by line in reverse order.
List all open ports
netstat -ltn -- all process that listens on tcp ports
-udp|-utroub
--tcp|-t
--listeningtro
--program|-p
Which process opens 9160
lsof -i :9160
lsof -p pid1
lsof -Pani -p PID
lsof /var/log/system.log
List opened files under a directory
lsof +D /var/log/
List files opened by a specific user
lsof -u user
lsof -u ^user
lsof -i
iptables
To get a complete presentation of the netfilter rules
iptables -vL -t filter
iptables -vL -t nat
iptables -vL -t mangle
iptables -vL -t raw
iptables -vL -t security
nohup someCommand > someFile.log 2>&1 &
sort | uniq -d
-u Only output lines that are not repeated in the input.
-d Only output lines that are repeated in the input.
-c count
Sort the output with the most frequent lines on top
sort FILE | uniq -c | sort -nr
find /usr -size +10M
find . -exec xxx {} \;
Find configuration data
find /etc -type f -exec grep -FHi "ENCRYPTION_PASSWORD" {} +
grep -r ENCRYPTION_PASSWORD /etc 2>/dev/null
find /etc -type f -print0 | xargs -0 grep ENCRYPTION_PASSWORD
Find biggest files
find ~/ -type f -exec du -Sh {} + | sort -rh | head -n 5
How long a command takes
time curl ""
List all functions
declare -f
declare -F - only list function names
declare -f function_name
Truncate a file
cat /dev/null > file
> file
Generate random number
/dev/random block when entropy pool is exhausted
/dev/urandom will not block
echo $RANDOM
od -An -N1 -i /dev/urandom
od -An -N2 -i /dev/urandom
for i in {1..5}; do echo $RANDOM; done
Display disk usage
du -sm
List all directories and their total size:
du -sh *
-s: Display an entry for each specified file. (Equivalent to -d 0)
Show only total for each directories
du -h -d 1
List hidden files: ls -a | grep "^\."
List files and sorted by size: ls -l | grep ^- | sort -nr
List link files: ls -l | grep '^l'
ls -l --block-size=M
Grep:
-c --count: Show count of matched lines
-E, --extended-regexp - same as egrep
-n, --line-number
-l, --files-with-matches
-L, --files-without-match
grep -E '^abc(worda|wordb)' /etc/group
-n or --line-number
-A NUM, --after-context=NUM
Print NUM lines of trailing context after matching lines.
-B NUM, --before-context=NUM
Print NUM lines of leading context before matching lines.
-C NUM, --context=NUM
Print NUM lines of output context.
-w - searched as a word
-o, --only-matching
Prints only the matching part of the lines.
-l -- only show matched file name
-w -- only if it's a whole word
-r -- recursively search
grep -r --exclude=\*.{html,htm,js} pattern rootdir
Grep file that contains binary data
cat -v tmp/test.log | grep regex
-v Display non-printing characters so they are visible.
Search specific line ranges:
sed -n 'startLine,endLinep' a.txt | grep XX
Use extended regular expression with grep -E
scroll results and pagination
grep ** | more/less
sed s/word1/word2/g fileName
Only display nth line: sed -n 'n p' file
Delete nth line: sed 'n d' file > newFile
Delte nth line in place: sed –i 'n d' file.txt
Remove last line: sed –i '$ d' file.txt
-i change in place
Delete first line: sed –i '$ d' file.txt
sed –i 'm,n d' file.txt
sed -i '' 's/original/replace/' file.txt
sed -i.bak ...
sed -n 'n p' file.txt | wc -c
-i extension | --in-place
Edit files in-place, saving backups with the specified extension. If a zero-length extension is given, no backup will be saved.
xargs
echo a b c | xargs echo
find /tmp -name "*.bk" -type f -print | xargs /bin/rm -f
find /tmp -name "*.bk" -print0 | xargs -0 -I {} mv {} ~/bk.files
-- better: find /tmp -depth -name "*.bk" -type f -delete
find /tmp -name "*.bk" -print0 | xargs -0 -I file mv file ~/bk.files
cut -d: -f1 < /etc/passwd | sort | xargs echo
-I replstr
--null, -0 - handle spaces in file name
Change xargs to expect NUL (``\0'') characters as separators, instead of spaces and newlines. This is expected to be used in concert with the -print0 function in find
less +F the.log
Ctrl+c to normal less mode
pv - monitor the progress of data through a pipe
pv the.gz | gunzip
jq - sed for JSON
curl the_url | jq
Scp copy from local to remote:
scp /file/to/send username@remote:/where/to/put
Remote to local:
scp username@remote:/file/to/send /where/to/put
Send files between two remote hosts:
scp username@remote_1:/file/to/send username@remote_2:/where/to/put
Copy file from remote host to local via gateway
scp -o "ProxyCommand ssh $USER@$bastion-host nc $destinationHost 22" $USER@$destinationHost:/home/$USER/heapdump.hprof heapdump.hprof
Copy file from local to remote host via gateway
scp -o "ProxyCommand ssh $USER@$bastion-host nc $destinationHost 22" heapdump.hprof $USER@$destinationHost:/home/$USER/heapdump.hprof
Netcat - nc
Listening on server
nc -l 2389 > test
nc -k -l 2389 - server would stay up
Connect to server on specific port
cat testfile | nc remoteHost 2389
Port Scanning
nc -zv remoteHost 20-30
Bulk rename files
brew install rename
rename -n -v 's/\.csv$/\.json/' *.csv
-n: --just-print/--dry-run
Brace Expansion
echo a{d,c,b}e
sleep 10 - sleep 10 seconds
wait pid - wait process finish
command &
wait $!
Find out current working directory of a running process
pwdx $PID
lsof -p $PID | grep cwd
readlink -e /proc/$PID/cwd
Setting an environment variable for one command only
FOO=bar bash -c 'somecommand someargs | somecommand2'
(export FOO=bar ; somecommand someargs | somecommand2)
Change working directory for current command only
(cd SOME_PATH && exec_some_command)
Check Linux System Info
lscpu
free -t -m
cat /proc/pid/smaps
pmap pid | grep total
uptime
sar
jstack -m
pstack
top
top -p PID
-on mac: top -pid PID
top -c or Press 'c' in top view: to show full command
top -H -p $pid
sort on other fields (default by cpu)
Press "SHIFT + F" and Select your choice below and press ENTER.
Get the hostname of remote server
host ip-address
Check system time zone
date
date +%Z
cat /etc/localtime
Create zip file
gzip -k the-file
- without the tar, -k: keep the original file
tar -czf my.tar.gz the-folder_or_file
gunzip file.gz
gzip -d file.gz
unzip –t file.zip
test whether zipfile is corrupted or not
awk, gawk
gawk 'match($0, pattern, ary) {print ary[1]}'
vi
Count the number of occurrences of a word
:%s/pattern//ng
:set all
- (no)nu, (no)ic,
Compound search on multiple lines
/pattern1/;/pattern2/
Bookmark
MA -> `A -> ``
dd, 5dd
d$ - delete to end of line
d0 - delete to beginning of line
1,$d - delete all
1,.d - delete to beginning of file
.,$d - delete to end of file
Y - copy
- p pastes after the cursor position
- P pastes before.
5Y
Y$ - the end of the line
G - go to the last line
ZZ in command line - :wq to exit vi
append a file to current file
:r file2
Misc
ps -ef | grep PROCESS | grep -v grep | awk '{print $2}' | xargs kill -9
tail **/*.log
cp
cp --parents a/b/c existing_dir
--no-target-directory | -T
clear log without delete it
cp /dev/null filename
> filename
su different_user -c "command"
mmv - Mass Move and rename
mmv "*.csv" "#1.xls"
To install mmv
yum install -y http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-1.el7.nux.noarch.rpm
yum install mmv
Compare difference of two folders
diff -rq folder1 folder2
apropos - search the whatis database for strings
apropos "kill process"
unzip '*.zip'
unzip *.zip would fail with error: "caution: filename not matched"
gunizp *.gz - don't add ' or ""
Add text to the beginning of a file
echo 'task goes here' | cat - todo.txt > temp && mv temp todo.txt
Java
Use jstack to generate thread dump
nohup jmap -F -dump:format=b,file=/root/heapdump.hprof pid &
Commands for troubleshooting
find class in jars
find . -name "*.jar" | xargs grep Hello.class
Search Contents of .jar Files for Specific String
gfind . -iname '*.jar' -printf "unzip -c %p | grep -q 'string_to_search' && echo %p\n" | sh
yum -y install java8-server-jre.x86_64 --nogpgcheck yum repolist
yum-config-manager --disable \*
yum-config-manager --add-repo repo_url
sudo without password
echo 'username ALL=(ALL) NOPASSWD: ALL' >> /etc/sudoers
sed -i 's/.*requiretty$/#Defaults requiretty/' /etc/sudoers
permission denied when run sudo with redirection
- Output redirection (via the > operator) is done by the shell, not by echo.
sudo bash -c "echo 'net.ipv6.conf.all.disable_ipv6 = 1' >>/etc/sysctl.conf"
Find hostname of remote ip address
host $ip
nslookup $ip
VI
:set ic|noic
Resources
Google Shell Style Guide
Ctrl + a - Move to the start of line
Ctrl + e - Move to the end of line
Clear the screen: Ctrl + l
Search as you type. Ctrl + r and type the search term; Repeat Ctrl + r to loop through results.
tac: print a file line by line in reverse order.
List all open ports
netstat -ltn -- all process that listens on tcp ports
-udp|-utroub
--tcp|-t
--listeningtro
--program|-p
Which process opens 9160
lsof -i :9160
lsof -p pid1
lsof -Pani -p PID
lsof /var/log/system.log
List opened files under a directory
lsof +D /var/log/
List files opened by a specific user
lsof -u user
lsof -u ^user
lsof -i
iptables
To get a complete presentation of the netfilter rules
iptables -vL -t filter
iptables -vL -t nat
iptables -vL -t mangle
iptables -vL -t raw
iptables -vL -t security
sort | uniq -d
-u Only output lines that are not repeated in the input.
-d Only output lines that are repeated in the input.
-c count
Sort the output with the most frequent lines on top
sort FILE | uniq -c | sort -nr
find . -exec xxx {} \;
Find configuration data
find /etc -type f -exec grep -FHi "ENCRYPTION_PASSWORD" {} +
grep -r ENCRYPTION_PASSWORD /etc 2>/dev/null
find /etc -type f -print0 | xargs -0 grep ENCRYPTION_PASSWORD
Find biggest files
find ~/ -type f -exec du -Sh {} + | sort -rh | head -n 5
How long a command takes
time curl ""
List all functions
declare -f
declare -F - only list function names
declare -f function_name
Truncate a file
cat /dev/null > file
> file
Generate random number
/dev/random block when entropy pool is exhausted
/dev/urandom will not block
echo $RANDOM
od -An -N1 -i /dev/urandom
od -An -N2 -i /dev/urandom
for i in {1..5}; do echo $RANDOM; done
Display disk usage
du -sm
List all directories and their total size:
du -sh *
-s: Display an entry for each specified file. (Equivalent to -d 0)
Show only total for each directories
du -h -d 1
List hidden files: ls -a | grep "^\."
List files and sorted by size: ls -l | grep ^- | sort -nr
List link files: ls -l | grep '^l'
ls -l --block-size=M
find . -type d -maxdepth 1 -name "H2*"
ls -d H2*/
-c --count: Show count of matched lines
-E, --extended-regexp - same as egrep
-n, --line-number
-l, --files-with-matches
-L, --files-without-match
grep -E '^abc(worda|wordb)' /etc/group
-n or --line-number
-A NUM, --after-context=NUM
Print NUM lines of trailing context after matching lines.
-B NUM, --before-context=NUM
Print NUM lines of leading context before matching lines.
-C NUM, --context=NUM
Print NUM lines of output context.
-w - searched as a word
-o, --only-matching
Prints only the matching part of the lines.
-l -- only show matched file name
-w -- only if it's a whole word
-r -- recursively search
grep -r --exclude=\*.{html,htm,js} pattern rootdir
Grep file that contains binary data
cat -v tmp/test.log | grep regex
-v Display non-printing characters so they are visible.
sed -n 'startLine,endLinep' a.txt | grep XX
Use extended regular expression with grep -E
scroll results and pagination
grep ** | more/less
sed s/word1/word2/g fileName
Only display nth line: sed -n 'n p' file
Delete nth line: sed 'n d' file > newFile
Delte nth line in place: sed –i 'n d' file.txt
Remove last line: sed –i '$ d' file.txt
-i change in place
Delete first line: sed –i '$ d' file.txt
sed –i 'm,n d' file.txt
sed -i '' 's/original/replace/' file.txt
sed -i.bak ...
sed -n 'n p' file.txt | wc -c
-i extension | --in-place
Edit files in-place, saving backups with the specified extension. If a zero-length extension is given, no backup will be saved.
xargs
echo a b c | xargs echo
find /tmp -name "*.bk" -type f -print | xargs /bin/rm -f
find /tmp -name "*.bk" -print0 | xargs -0 -I {} mv {} ~/bk.files
-- better: find /tmp -depth -name "*.bk" -type f -delete
find /tmp -name "*.bk" -print0 | xargs -0 -I file mv file ~/bk.files
cut -d: -f1 < /etc/passwd | sort | xargs echo
-I replstr
--null, -0 - handle spaces in file name
Change xargs to expect NUL (``\0'') characters as separators, instead of spaces and newlines. This is expected to be used in concert with the -print0 function in find
less +F the.log
Ctrl+c to normal less mode
pv - monitor the progress of data through a pipe
pv the.gz | gunzip
jq - sed for JSON
curl the_url | jq
Scp copy from local to remote:
scp /file/to/send username@remote:/where/to/put
Remote to local:
scp username@remote:/file/to/send /where/to/put
Send files between two remote hosts:
scp username@remote_1:/file/to/send username@remote_2:/where/to/put
scp -o "ProxyCommand ssh $USER@$bastion-host nc $destinationHost 22" $USER@$destinationHost:/home/$USER/heapdump.hprof heapdump.hprof
Copy file from local to remote host via gateway
scp -o "ProxyCommand ssh $USER@$bastion-host nc $destinationHost 22" heapdump.hprof $USER@$destinationHost:/home/$USER/heapdump.hprof
Netcat - nc
Listening on server
nc -l 2389 > test
nc -k -l 2389 - server would stay up
Connect to server on specific port
cat testfile | nc remoteHost 2389
Port Scanning
nc -zv remoteHost 20-30
Bulk rename files
brew install rename
rename -n -v 's/\.csv$/\.json/' *.csv
-n: --just-print/--dry-run
Brace Expansion
echo a{d,c,b}e
sleep 10 - sleep 10 seconds
wait pid - wait process finish
command &
wait $!
Find out current working directory of a running process
pwdx $PID
lsof -p $PID | grep cwd
readlink -e /proc/$PID/cwd
Setting an environment variable for one command only
FOO=bar bash -c 'somecommand someargs | somecommand2'
(export FOO=bar ; somecommand someargs | somecommand2)
(cd SOME_PATH && exec_some_command)
Check Linux System Info
lscpu
free -t -m
cat /proc/pid/smaps
pmap pid | grep total
uptime
sar
jstack -m
pstack
top
top -p PID
-on mac: top -pid PID
top -c or Press 'c' in top view: to show full command
top -H -p $pid
sort on other fields (default by cpu)
Press "SHIFT + F" and Select your choice below and press ENTER.
Get the hostname of remote server
host ip-address
Check system time zone
date
date +%Z
cat /etc/localtime
Create zip file
gzip -k the-file
- without the tar, -k: keep the original file
tar -czf my.tar.gz the-folder_or_file
gunzip file.gz
gzip -d file.gz
unzip –t file.zip
test whether zipfile is corrupted or not
awk, gawk
gawk 'match($0, pattern, ary) {print ary[1]}'
vi
Count the number of occurrences of a word
:%s/pattern//ng
:set all
- (no)nu, (no)ic,
Compound search on multiple lines
/pattern1/;/pattern2/
Bookmark
MA -> `A -> ``
dd, 5dd
d$ - delete to end of line
d0 - delete to beginning of line
1,$d - delete all
1,.d - delete to beginning of file
.,$d - delete to end of file
Y - copy
- p pastes after the cursor position
- P pastes before.
5Y
Y$ - the end of the line
G - go to the last line
ZZ in command line - :wq to exit vi
append a file to current file
:r file2
Misc
ps -ef | grep PROCESS | grep -v grep | awk '{print $2}' | xargs kill -9
tail **/*.log
cp
cp --parents a/b/c existing_dir
--no-target-directory | -T
clear log without delete it
cp /dev/null filename
> filename
su different_user -c "command"
mmv - Mass Move and rename
mmv "*.csv" "#1.xls"
To install mmv
yum install -y http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-1.el7.nux.noarch.rpm
yum install mmv
Compare difference of two folders
diff -rq folder1 folder2
apropos - search the whatis database for strings
apropos "kill process"
unzip '*.zip'
unzip *.zip would fail with error: "caution: filename not matched"
gunizp *.gz - don't add ' or ""
Add text to the beginning of a file
echo 'task goes here' | cat - todo.txt > temp && mv temp todo.txt
Java
Use jstack to generate thread dump
nohup jmap -F -dump:format=b,file=/root/heapdump.hprof pid &
Commands for troubleshooting
find class in jars
find . -name "*.jar" | xargs grep Hello.class
Search Contents of .jar Files for Specific String
gfind . -iname '*.jar' -printf "unzip -c %p | grep -q 'string_to_search' && echo %p\n" | sh
yum -y install java8-server-jre.x86_64 --nogpgcheck yum repolist
yum-config-manager --disable \*
yum-config-manager --add-repo repo_url
sudo without password
echo 'username ALL=(ALL) NOPASSWD: ALL' >> /etc/sudoers
sed -i 's/.*requiretty$/#Defaults requiretty/' /etc/sudoers
permission denied when run sudo with redirection
- Output redirection (via the > operator) is done by the shell, not by echo.
sudo bash -c "echo 'net.ipv6.conf.all.disable_ipv6 = 1' >>/etc/sysctl.conf"
Find hostname of remote ip address
host $ip
nslookup $ip
VI
:set ic|noic
Resources
Google Shell Style Guide
Subscribe to:
Posts (Atom)