linuxcmds.txt

tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ	Convert lower case to upper case
tr '{}' '()' < inputfile > outputfile	Translate braces into parenthesis
echo "This is for testing" | tr [:space:] '\t'	Translate white-space to tabs
echo "This   is   for    testing" | tr -s [:space:]
Squeeze repetition of characters using -s
echo "the geek stuff" | tr -d 't'	Delete specified characters using -d option
echo "my username is 432234" | tr -cd [:digit:]	Complement the sets using -c option
tr -cd [:print:] < file.txt	Remove all non-printable character from a file
tr -s '\n' ' ' < file.txt	Join all the lines in a file into a single line

 traceroute -T oracle_host -p jdbc_port
  ldap
/usr/sbin/slapd  -h "ldapi:/// ldap:///" -d stats &

host--dns resolve linux
nslookup-- dns resolve win

Show current routing table	$ route –n or ip route
Add static route	$ route add -net address or ip route add 
Delete static route	$ route del -net address or ip route del 

ethtool---	Queries network interfaces and can also set various parameters such as the speed
netstat------	Displays all active connections and routing tables. Useful for monitoring performance and troubleshooting
nmap---------Scans open ports on a network. Important for security analysis
tcpdump	-----Dumps network traffic for analysis
iptraf	----Monitors network traffic in text mode
mtr	---------Combines functionality of ping and traceroute and gives a continuously updated display
dig	-----------Tests DNS workings. A good replacement for host and nslookup
curl ifconfig.co----public ip from server

if statement

-e file	Checks if the file exists.
-d file	Checks if the file is a directory.
-f file	Checks if the file is a regular file (i.e. not a symbolic link, device node, directory, etc.)
-s file	Checks if the file is of non-zero size.
-g file	Checks if the file has sgid set.
-u file	Checks if the file has suid set.
-r file	Checks if the file is readable.
-w file	Checks if the file is writable.
-x file	Checks if the file is executable.
-n
   string is not null.

-z
  string is null, that is, has zero length
  
  
echo ` hostname -f ` `pip3 list installed|grep six ` ` date `
echo $(hostname -f) $(pip3 list installed|grep six) $(date)

both giv same output -  <hostanme> six (1.10.0) <date command output> - in one line

to change the max number of pids use command - sudo sysctl -w kernel.pid_max=4194304
u can chk this is in file /proc/sys/kernel/pid_max

    command to check the ip of the machine the user logged in from - last <username>|grep "still"
    command to check the ip of the machine the user logged in from - last <username>|grep "still" - this will giv u ip
to get teh hostname from ip - nslookup <ip> or dig -x ip 


#find /home/daygeek/shell-script -type f -mtime -15 -ls - to list files that are modified from 15 days
#ps -Ao user,uid,comm,pid,pcpu,args --sort=-pcpu | head -n 6 - to check process with high cpu
#find / -size +1M -exec du -sh {} \ - to list files and file sizes of files grated than 1 mb
#nethogs -a - to monitor the network usage by a process
#nload  - to monitor network traffic on a node
#htop - better than top