[one day learning awk] function and user-defined function

Built in functions

sin(expr) Sine

cos(expre) cosine

atan2(y,x) Anyway

exp(expr) Index

log(expr) logarithm  

sqrt(expr) square root

int(expr) Integers

rand random number

srand([expr]) random number

Array sorting

awk 'BEGIN{a[0] = "c"; a[1] = "b"; a[2] = "a"; asort(a); for (ele in a){print a[ele]}}'

Sort by array index

awk 'BEGIN{a[0] = "c"; a[1] = "b"; a[2] = "a"; asorti(a); for (ele in a){print a[ele]}}'

String substitution gsub("pattern", "content",  str)

Replace only once sub("pattern", "content",  str)

String search index(str, "pattern")

If found, return to the location , Otherwise return to 0

String length length 

Regular matching match(str, patten)

String segmentation split(str, array, "patten")

String to number

awk 'BEGIN{str = "123"; print strtonum(str)}' 

String interception substr(str, index, len)

toggle case tolower(str) toupper(str)

Don't change the original string

Time stamp

awk 'BEGIN{print SYSTIME() }' 

Print time

awk 'BEGIN {
   print strftime("Time=%m/%d/%Y %H:%M:%S", SYSTIME())
}'

Get a row

Custom function

Output redirection ( Additional )

Output redirection （ Cover ）