linux – AgileAdam.com

Our business is located in Maine (same timezone as New York; we set clocks back one hour in the Fall and ahead one hour in the Spring)
Server A uses ET (automatically adjusts to UTC-4 in the summer, and UTC-5 in the winter)
Server B uses UTC (not affected by Daylight Saving Time) – we cannot control the timezone of this server

We want to ensure both servers are always referencing, figuratively, the same clock on the wall in Maine.

Here’s what we can do to make sure the timing of cron jobs on Server B (UTC) match the changing times of Server A (ET).

# Every day at 11:55pm EST (due to conditional, commands only run during Standard Time (fall/winter)
55 4 * * * [ `TZ=America/New_York date +\%Z` = EST ] && php artisan scrub-db >/dev/null 2>&1

# Every day at 11:55pm EDT (due to conditional, commands only run during Daylight Saving Time (spring/summer)
55 3 * * * [ `TZ=America/New_York date +\%Z` = EDT ] && php artisan scrub-db >/dev/null 2>&1

# Every day at 11:55pm EST (due to conditional, commands only run during Standard Time (fall/winter)

55 4 * * * [ `TZ=America/New_York date +\%Z` = EST ] && php artisan scrub-db >/dev/null 2>&1

# Every day at 11:55pm EDT (due to conditional, commands only run during Daylight Saving Time (spring/summer)

55 3 * * * [ `TZ=America/New_York date +\%Z` = EDT ] && php artisan scrub-db >/dev/null 2>&1

Only one of the php artisan scrub-db commands will execute, depending on the time of year.

After a quick Google search for “ls permissions octal” I found a very handy alias to put in my .bashrc. Not only is it handy to see the OCTAL value of the permissions for each file/dir, it will undoubtedly help you more quickly recognize/interpret the normal ls -al output.

alias lso="ls -alG | awk '{k=0;for(i=0;i<=8;i++)k+=((substr(\$1,i+2,1)~/[rwx]/)*2^(8-i));if(k)printf(\" %0o \",k);print}'"

1	alias lso="ls -alG \| awk '{k=0;for(i=0;i<=8;i++)k+=((substr(\$1,i+2,1)~/[rwx]/)*2^(8-i));if(k)printf(\" %0o \",k);print}'"

Example usage:

mycomp:~ adam$ lso
755 drwxr-xr-x 15 adam staff 510 Dec 6 02:47 .vim
644 -rw-r--r-- 1 adam staff 1136 Dec 18 16:55 .vim_mru_files
600 -rw------- 1 adam staff 13665 Dec 18 16:56 .viminfo

mycomp:~ adam$ lso

755 drwxr-xr-x 15 adam staff 510 Dec 6 02:47 .vim

644 -rw-r--r-- 1 adam staff 1136 Dec 18 16:55 .vim_mru_files

600 -rw------- 1 adam staff 13665 Dec 18 16:56 .viminfo

You can also type (or paste) this slightly different version into terminal:

ls -l | awk '{k=0;for(i=0;i<=8;i++)k+=((substr($1,i+2,1)~/[rwx]/)*2^(8-i));if(k)printf("%0o ",k);print}'

1	ls -l \| awk '{k=0;for(i=0;i<=8;i++)k+=((substr($1,i+2,1)~/[rwx]/)*2^(8-i));if(k)printf("%0o ",k);print}'

Handling Daylight Saving Time in Cron Jobs

“755”-style permissions with ‘ls’