bash - How can I use addhour for custom date? -

i have string conf file (lets call example date1):

#!/bin/bash # example date1="201605250925"  datenow="$(date +%y%m%d%h%m -d "+1hour")"  date2=$(date +%y%m%d%h%m -d "$date1 + 1hour") # not work? echo "$date1 --> $date2" # work! echo "$date1 --> $datenow" 

i need add 1 hour. getting error this:

date: invalid date `201605250925 + 1hour' 

but work datenow.

how can user addhour custom date format string?

you need format meets command date expectations, like:

2016-05-25 09:25 

the space denote start of time , time format hh:mm.
comes international iso 8601, using space instead of t.

if format fixed, can use bash internal capacities (no external command except date used) change this:

#!/bin/bash d1="201605250925"  dc="${d1:0:8} ${d1:8:2}:${d1:10:2}+0" d2=$(date +'%y%m%d %h:%m' -ud "$dc + 1 hour" ) echo "$d2" 

or posixly (dash) no call needed sed, awk or cut (faster):

#!/bin/dash d1="201605250925"  dt=${d1##????????}  dc="${d1%%"$dt"} ${dt%%??}:${dt##??}+0" d2=$(date -ud "$dc + 1 hour" +'%y%m%d %h:%m') echo "$d2" 

---

20160525 10:25 

the inclusion of +0 after time in dc: 20160525 09:25+0
ensure date interpret time offset 0 (utc).

the use of option -u date ensure value read in utc change in utc, avoiding daylight correction or local time change.