difference :: cat file_1 & cat < f_1

tushar_pandey · 08-15-2012, 09:16 PM

what is the difference between cat f_1 & cat < f_1

i am asking this question because , i am not getting the reason behind , why cat < - is not working ! thats why i am asking the difference !

pixellany · 08-15-2012, 09:24 PM

On my system, these 2 commands do the same thing:
cat filename
cat < filename

tushar_pandey · 08-15-2012, 09:44 PM

pixellany , in my system also ,

think about this ,

Code:

cat -

works same as

Code:

cat

, and i think "-" is taking input from keyboard !
and now think about this ,

Code:

cat < from_file_1

, and here input is coming from_file_1 ,

now why ,

Code:

cat < -

not working

chrism01 · 08-16-2012, 07:02 AM

Try

Code:

cat -

David the H. · 08-16-2012, 09:19 AM

cat is a command that can read either from a file or from stdin. When you call "cat filename", it's accessing the file directly. When you use "cat <filename", you're asking the shell to send the contents of the file into cat's stdin.

The end effect is the same, but avoiding the redirection is likely slightly more efficient.

Finally, in many commands "-" can be used as a substitute for a filename to mean "read from stdin". This is instead of "<", not in addition to it.