Shell Programming and Scripting

Hi,

Do you mind explaining use of

Code:

> 0

in

Code:

getline < "f1" > 0

The getline function returns 1 for successful input, zero for end-of-file, and −1 for an error. So:

Code:

while((getline < "f1") > 0) x[$2]=$0

reads successive lines from a file named f1 until EOF or a read error is detected. And, for each line successfully read from that file, an element in the array x with the array index specified by the 2nd field found in that line is created or updated to have the value specified by the entire contents of that line.

IMHO you are mixing operator overloading with operator precedence...the left arrow stands for "input" while the right arrow tests for "greater than" is evident from the program's context and the rules of precedence and associativity have nothing to do with the interpretation of these operators...that being said the implied parenthesization of (getline < "f1" > 0) is ((getline < "f1") > 0)

---------- Post updated at 11:49 PM ---------- Previous update was at 11:42 PM ----------

You need "> 0" because if file f1 doesnt exist getline returns -1 which in awk terms is true thereby producing an infinite loop...