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Bash script time script

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# 8  
Old 12-22-2016
Hi Scrutinizer,
Yes, I apologize. Before the standards were there for the shell, at least one shell treated the simple command:
Code:
a=1 b=2 c=3

as the command c=3 with the other two assignments being treated as a command prefix (so a and b did not end up being present in the current shell execution environment; they were only available in the execution environment of the assignment command assigning a value to c). I don't remember if any shell still has this strange behavior, but since we're talking about POSIX shells in this thread it doesn't matter. With any POSIX conforming shell all three of the following produce the same results:
Code:
a=1 b=2 c=3

Code:
a=1;b=2;c=3

Code:
a=1
b=2
c=3

These 2 Users Gave Thanks to Don Cragun For This Post:
rbatte1 SkySmart
# 9  
Old 12-22-2016
thanks everyone. it works now! Smilie
# 10  
Old 12-22-2016
This should be basic /bin/sh compatible

Code:
#!/bin/sh

# turn seconds into real measurable time

num=${1:-0}
min=0
hour=0
day=0
if [ $num -gt 59 ]
then
    sec=`expr $num % 60`
    num=`expr $num / 60`
    if [ $num -gt 59 ]
    then
        min=`expr $num % 60`
        num=`expr $num / 60`
        if [ $num -gt 23 ]
        then
            hour=`expr $num % 24`
            day=`expr $num / 24`
        else
            hour=$num
        fi
    else
        min=$num
    fi
else
    sec=$num
fi
echo "$day"d,"$hour"h,"$min"m,"$sec"s

or it could be simplified a little (at the expense of some performance):

Code:
#!/bin/sh

# turn seconds into real measurable time

num=${1:-0}
day=`expr $num / 86400`
num=`expr $num % 86400`
hour=`expr $num / 3600`
num=`expr $num % 3600`
min=`expr $num / 60`
sec=`expr $num % 60`
echo "$day"d,"$hour"h,"$min"m,"$sec"s

Last edited by Chubler_XL; 12-22-2016 at 11:10 PM..
# 11  
Old 12-23-2016
Quote:
Originally Posted by Don Cragun
[..] With any POSIX conforming shell all three of the following produce the same results:
Code:
a=1 b=2 c=3

Code:
a=1;b=2;c=3

Code:
a=1
b=2
c=3

Thanks for looking into this and confirming this..

One possible caveat to note is that the order in which these assignments are being made within a single simple command is not defined by the standards as far as I know, so if assignments are interdependent then I think it may be best to use separate simple commands.

For example:
Code:
a=1 b=$a

will typically produce a=1 and b=1, but I do not think it is guaranteed by the standards. It might also be a=1 and b="", which would be the case if it is done right to left or in arbitrary order. Even though I have only come across implementations that go left to right.. ( Simple Commands )
Last edited by Scrutinizer; 12-23-2016 at 02:39 AM..
These 2 Users Gave Thanks to Scrutinizer For This Post:
rbatte1 SkySmart
# 12  
Old 12-23-2016
Quote:
Originally Posted by Scrutinizer
... ... ...

One possible caveat to note is that the order in which these assignments are being made within a single simple command is not defined by the standards as far as I know, so if assignments are interdependent then I think it may be best to use separate simple commands.

For example:
Code:
a=1 b=$a

will typically produce a=1 and b=1, but I do not think it is guaranteed by the standards. It might also be a=1 and b="", which would be the case if it is done right to left or in arbitrary order. Even though I have only come across implementations that go left to right.. ( Simple Commands )
Hi Scrutinizer,
The standards do guarantee it... From The Commands and Utilities Volume of the 2016 edition of the POSIX Standards:
Quote:
2.9.1 Simple Commands
A ‟simple command'' is a sequence of optional variable assignments and redirections, in any sequence, optionally followed by words and redirections, terminated by a control operator.

When a given simple command is required to be executed (that is, when any conditional construct such as an AND-OR list or a case statement has not bypassed the simple command), the following expansions, assignments, and redirections shall all be performed from the beginning of the command text to the end:
From the beginning ... to the end in shell scripts means left to right. (In some other places in the standard referring to text that could be from a language that is written from right to left, beginning to end means left to right for text that is written from left to right and it means right to left for text that is written from right to left.)
These 3 Users Gave Thanks to Don Cragun For This Post:
rbatte1 Scrutinizer SkySmart
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