https://qiita.com/Ets/items/cd3baa5cecbf553f822d

example.sh

#!/bin/bash
t() {
  #DATETIME_FORMAT=$(date --iso-8601="minutes")
  DATETIME_FORMAT=$(date +%T)
  echo -n "$DATETIME_FORMAT [info]:"
  "$@"
 return $?
}
t echo "A"
t echo "A"
t echo "A"
t echo "A"
t echo "A"
t echo "A"
t echo "A"
t echo "A"
$ bash example.sh
15:27:56 [info]:A
15:27:56 [info]:A
15:27:56 [info]:A
15:27:56 [info]:A
15:27:56 [info]:A
15:27:56 [info]:A
15:27:56 [info]:A
15:27:56 [info]:A

logging.sh

#!/bin/bash

DATETIME_FORMAT=$(date "+%Y-%m-%dT%H:%M:%S%z")

set_datetime() {
  echo -n "$DATETIME_FORMAT [info]:"
  "$@"
 return $?
}
logger() {
  echo $(set_datetime "$@")
}

timestamp

#!/bin/bash

t() {
  echo -n "$(date --iso-8601="minutes") [info]:"
  "$@"
 return $?
}