TIL 1:

Incrementing times with the date command

files to shows which lost them when we migrated to the current static

site.

but to make this check I need to wait for the next update of the static

site.

the site every three hours. Each show page shows the refresh time in UTC

form in the header.

next refresh time in my timezone from the previous refresh time.

after the -d option (or using the

alternative--date=STRING option). The contents of the

STRING here are very flexible but quite complex since you

can include time zone data, offsets, day and month names, etc. See the

links below for links to the GNU manual.

got the wrong answer (using the output format +%T which

writes the time in a default form):

$ date -d '16:27:16 + 3 hours' +%T

15:27:16

these date parameters is obviously confused. The second try included the

time zone after the time, and worked better, but is a little

confusing:

$ date -d '16:27:16 UTC + 3 hours' +%T

20:27:16

command has added three hours to the UTC date to get 19:27:16, but since

I am in the UK, which is in DST (called BST - British Summer Time - UTC

plus 1 hour), an hour is added.

time:

$ date -u -d '16:27:16 UTC + 3 hours' +%T

19:27:16

script would have been better):

$ current='06:27:55'

$ next=$(date -u -d "${current}UTC + 3 hours 3 minutes" +%T); echo "$next UTC / $(date -d "${next} UTC" +'%T %Z')"

09:30:55 UTC / 10:30:55 BST

$ current=$next

$ next=$(date -u -d "${current}UTC + 3 hours 3 minutes" +%T); echo "$next UTC / $(date -d "${next} UTC" +'%T %Z')"

12:33:55 UTC / 13:33:55 BST

$ current=$next

$ next=$(date -u -d "${current}UTC + 3 hours 3 minutes" +%T); echo "$next UTC / $(date -d "${next} UTC" +'%T %Z')"

15:36:55 UTC / 16:36:55 BST

TIL 1: Links

Coreutils manual

context

Print or set system date and time

input formats (The quotation at the start of this section of the

manual is quite interesting!)

examples

TIL 2: Merging lines of

files with paste

generate a list of show numbers separated by commas. In the past I have

loaded these into a Bash array and turned them into a comma-delimited

string, using the parameter substitution capabilities of Bash which can

add a comma to each element. The trouble with this is that it leaves a

trailing comma which has to be removed. I stumbled upon

paste as an alternative way of doing this.

Coreutils group. This one merges lines of files. Its synopsis

is:

paste [OPTION]... [FILE]...

provided as an argument, by default separated by TABs, and writes them

to standard output. This means it produces lines consisting of the first

line from each of the files, separated by tabs, then the second lines,

and so on.

- (hyphen) as the file name.

--delimiters=LIST option. The use of a list of delimiters

causes the characters in the list to be used sequentially for each

delimiter.

file provides a column.

--serial option. Here the lines from one file at a time are

merged - the files are processed serially rather than in

parallel.

comma-delimited list I wanted by using the options -s and

-d ',':

$ printf '%s\n' {1..10} | paste -s -d, -

1,2,3,4,5,6,7,8,9,10

echo {1..10} because all the numbers will be written to one

line rather than being the separate lines that paste

requires.

process substitution expressions:

$ paste -s -d, <(printf '%s\n' {1..10})

1,2,3,4,5,6,7,8,9,10

process substitution expressions where each is seen as a

file:

$ paste -d'|' <(printf '%d\n' {1..7}) <(printf '%s\n' {A..G}) <(printf '%d\n' {100..106})

1|A|100

2|B|101

3|C|102

4|D|103

5|E|104

6|F|105

7|G|106

$ paste -s -d'|' <(printf '%d\n' {1..7}) <(printf '%s\n' {A..G}) <(printf '%d\n' {100..106})

1|2|3|4|5|6|7

A|B|C|D|E|F|G

100|101|102|103|104|105|106

numbers to another script which will accept a CSV list as an

option:

$ echo "select episode_id from repairs where repair_date is null order by episode_id desc limit 5" |\

sqlite3 -list ~/HPR/InternetArchive/ia.db | paste -s -d',' -

1959,1952,1951,1946,1941

TIL 2: Links

Coreutils manual

on fields

Merge lines of files