“/ dev / null”在shell命令的末尾是什么意思

Question

What is the difference between the following commands?

ssh myhostname "command1; command2;...commandn;" 2>/dev/null
ssh myhostname "command1; command2;...commandn;" 

1. what does 2> mean?

2. what does /dev/null mean? I read somewhere that result of command will be write to file /dev/null instead of console! Is it right? It seems strange for me that the name of file be null !

Answer 1

2> means "redirect standard-error" to the given file.

/dev/null is the null file. Anything written to it is discarded.

Together they mean "throw away any error messages".

Answer 2

1 is stdout. 2 is stderr.

Then sometimes you find 2>&1 , that means redirecting stderr to stdout.

Answer 3

'/dev/null' essentially means "into the void", discarded. The 2 you mention refers to error output, where it should be directed.

Answer 4

2> means sending standard error to something

/dev/null means a bin

Answer 5

1) Pipe everything on standard error to /dev/null (so ignore it and don't display it)

2) Dev null just points to nowhere, pipe anything to that, and it disappears.