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Top Forums Shell Programming and Scripting How to use a variable as a command option? Post 302603484 by quinestor on Thursday 1st of March 2012 06:20:26 AM
Old 03-01-2012
How to use a variable as a command option?

I am just learning shell scripting and already I found out I have the bad habit of thinking that it is similar to php or c.

I learned some basics and now encountered this problem:

On shell it is possible to type:

 
$ date --date="2009-10-10 09:08:34"
Sat Oct 10 09:08:34 CEST 2009

This tells date to output the date in that string in that default format. But now, I can't pass that string as a variable:

 
$ dateLabel="2009-10-10 09:08:34"
$ date --date=$dateLabel
date: the argument `09:08:34' lacks a leading `+';
when using an option to specify date(s), any non-option
argument must be a format string beginning with `+'
Try `date --help' for more information.

I thought the problem could be the quotes but I have the same result if I first set the variable to have quotes:

 
$ dateLabel="\"2009-10-10 09:08:34\""
$ date --date=$dateLabel
date: the argument `09:08:34"' lacks a leading `+';
when using an option to specify date(s), any non-option
argument must be a format string beginning with `+'
Try `date --help' for more information.

I just don't get it, is it like there is a different encoding for that blank space?

Anyone can help me?
 

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DP(8)                                                                [nmh-1.5]                                                               DP(8)

NAME
dp - parse dates 822-style SYNOPSIS
/usr/lib/mh/dp [-form formatfile] [-format string] [-width columns] [-version] [-help] dates ... DESCRIPTION
Dp is a program that parses dates according to the ARPA Internet standard. It also understands many non-standard formats, such as those produced by TOPS-20 sites and some UNIX sites using ctime(3). It is useful for seeing how nmh will interpret a date. The dp program treats each argument as a single date, and prints the date out in the official 822-format. Hence, it is usually best to enclose each argument in quotes for the shell. To override the output format used by dp, the -format string or -format file switches are used. This permits individual fields of the address to be extracted with ease. The string is simply a format string and the file is simply a format file. See mh-format(5) for the details. Here is the default format string used by dp: %<(nodate{text})error: %{text}%|%(putstr(pretty{text}))%> which says that if an error was detected, print the error, a `:', and the date in error. Otherwise, output the 822-proper format of the date. FILES
$HOME/.mh_profile The user profile PROFILE COMPONENTS
None SEE ALSO
ap(8), Standard for the Format of ARPA Internet Text Messages (RFC-822) DEFAULTS
`-format' default as described above `-width' default to the width of the terminal CONTEXT
None BUGS
The argument to the -format switch must be interpreted as a single token by the shell that invokes dp. Therefore, one must usually place the argument to this switch inside quotes. MH.6.8 11 June 2012 DP(8)
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