Shell Programming and Scripting

Hi, this question is quite basic.

I'm simply trying to understand what a call to sort, using no additional parameters, returns. "man sort" reports it will return:
"sorted concatenation of all FILE(s)"

so what is a "sorted concatenation"? Does it sort first by the first column, then by the second, etc? Or just on the first?

Really, I have a very large file and I only need it sorted on the first column. So will:
sort -k1,1 myFile.txt
be faster than:
sort myFile.txt ?

Thanks..

Looking at just the first field would be faster than looking at the whole line and figuring out the sort order...so yes "sort -k1,1 myFile.txt" would be faster than "sort myFile.txt"...and you should double check it by timing the two sorts.