awk: try to convert timestamp string to unix epoch time

Question

I try to convert a timestamp string to unix epoch time using awk but fail after several attempts.

$ echo "2024-04-16 16:32:38.108580" | awk '{ epoch = mktime(gensub(/[:-]/, " ", "g", $1)) + substr($1, index($1, ".")+1) ; print epoch }'
2023

Answer 1

mktime() is looking for input of the format YYYY MM DD HH MM SS so in this case we want to:

### convert this:

2024-04-16 16:32:38.108580

### to this:

2024 04 16 16 32 38

We can do this a couple ways:

gensub(/[:-]|[.].*$/, " ", "g")
  gsub(/[:-]|[.].*$/, " ")

Since I don't designate a field or variable to operate on the functions operate on the entire line (ie, $0).

OP's code only performs operations on the first white space delimited field ($1) which in this case is 2024-04-16. OP will either need to designate the first 2 fields ($1 " " $2) or the whole line ($0 - default behavior if no field designated).

Since the sample input only has the 2 white space delimited fields we'll stick with processing the entire line ($0).

Pulling these changes into a new awk script:

### convert input to mktime() format:

$ echo "2024-04-16 16:32:38.108580" | awk '{ print gensub(/[:-]|[.].*$/, " ", "g") }'
2024 04 16 16 32 38

### convert to epoch seconds:

$ echo "2024-04-16 16:32:38.108580" | awk '{ print mktime(gensub(/[:-]|[.].*$/, " ", "g")) }'
1713303158

### reverse operation to verify we've got the correct epoch seconds

$ date '+%Y-%m-%d %H:%M:%S' -d @1713303158
2024-04-16 16:32:38

---

If we need to append the .108580 on the end we can re-use OP's substr( index() ) code as long as we remember to operate on the entire line ($0):

$ echo "2024-04-16 16:32:38.108580" | awk '{ print mktime(gensub(/[:-]|[.].*$/, " ", "g")) substr($0, index($0, ".")) }'
1713303158.108580