Linux Utilities

2015-03-01

network

curl

POST json data:

1	curl -H "Content-Type: application/json" -d '{"username":"xyz","password":"xyz"}' http://foo.com/api/login

Post a file:

1	curl -D - -F key1=value1 -F uploadedFile=@E:\abc.txt http://foo.com/post

For windows, single quotes around json did not work and I ended up escaping double quotes:

1	curl -X POST -H "Content-Type: application/json" -d "{ \"key1\": \"value1\" }" http://foo.com/api/method

text browsers

elinks, lynx, etc.

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Change Shell Prompt Color

2014-09-19

Normal user: vi ~/.bashrc

1	export PS1="\n\e[0;33m[\t \u@\h \W]\$ \e[m"

Root user (set as red #):

1	export PS1="\n\e[0;31m[\t \u@\h \W]\$ \e[m"

References:

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Verifying Which Ports Are Listening

2014-07-12

1 2	nmap -sT -O localhost netstat -tuplen

Troubleshooting:

This output shows the system is running portmap due to the presence of the sunrpc service. However, there is also a mystery service on port 834. To check if the port is associated with the official list of known services, type:

1	cat /etc/services \| grep 834

===>

1	netstat -anp \| grep 834

The command returns the following output:

tcp   0    0 0.0.0.0:834    0.0.0.0:*   LISTEN   653/ypbind

===>

1	lsof -i \| grep 834

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Keep A Process Running After Terminal Disconnected

2014-04-29

Senarino

To leave a process running during the night, and continue the work next morning.

Solution

nohup

1	nohup blah &

Substitute your process name for blah.

screen

screen is a powerful utility, which allows you to disconnect from the server while all of your processes continue to run.

%% js: Detach from a running screen session leaving it running in the background:

Control + A + D (not case sensitive)

%% Re-attach to a specific screen you’ve named:

screen -R somename

Useful screen commands:
List a particular users screen sessions:

screen -list username/ (the forward slash is important)

List your own active screen sessions:

screen -ls

Re-attach to a specific users screen and session:

screen -x username/shared-session

Start a screen session and give it a unique name:

screen -S somename

Detach from a running screen session leaving it running in the background:

Hit the key combination: Control + A/a + D/d (not case sensitive)

Re-attach to a specific screen you’ve named:

screen -R somename

Power detach a screen that you are logged into from another location:
This is helpful if you’ve been accidentally disconnected from ssh while in a remote screen session and it’s still attached.
screen -D somename

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