Re: Bash - an odd problem using sed or awk or for
On Sat, 2012-12-01 at 23:25 -0430, Patrick O'Callaghan wrote: > On Fri, 2012-11-30 at 21:37 -0700, Greg Woods wrote: > > On Thu, 2012-11-29 at 23:33 +, John Horne wrote: > > > > > (the '=' are not part of the variable) > > > abc def > > > > > > hijk > > > xyz > > > > > > > > > So in this case what is wanted is: > > > > > > > > > hijk > > > xyz > > > > > > > > > to be shown. > > > > echo "$XX" | sed -e '1,/^$/d' > > This will delete lines up to and including the first blank line. The > OP's problem statement isn't very clear, but I think he wants to delete > everything up to and including the last blank line, if any. > Correct. John. -- John Horne, Plymouth University, UK Tel: +44 (0)1752 587287Fax: +44 (0)1752 587001 -- users mailing list users@lists.fedoraproject.org To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org
Re: Bash - an odd problem using sed or awk or for
On Fri, 2012-11-30 at 21:37 -0700, Greg Woods wrote: > On Thu, 2012-11-29 at 23:33 +, John Horne wrote: > > > (the '=' are not part of the variable) > > abc def > > > > hijk > > xyz > > > > > > So in this case what is wanted is: > > > > > > hijk > > xyz > > > > > > to be shown. > > echo "$XX" | sed -e '1,/^$/d' This will delete lines up to and including the first blank line. The OP's problem statement isn't very clear, but I think he wants to delete everything up to and including the last blank line, if any. poc -- users mailing list users@lists.fedoraproject.org To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org
Re: Bash - an odd problem using sed or awk or for
On Thu, 2012-11-29 at 23:33 +, John Horne wrote: > (the '=' are not part of the variable) > abc def > > hijk > xyz > > > So in this case what is wanted is: > > > hijk > xyz > > > to be shown. echo "$XX" | sed -e '1,/^$/d' -- users mailing list users@lists.fedoraproject.org To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org
Re: Bash - an odd problem using sed or awk or for
On Fri, Nov 30, 2012 at 5:32 AM, John Horne wrote:
> On Thu, 2012-11-29 at 18:56 -0600, inode0 wrote:
>
>>
>> Oh, for a simple variable this should work
>>
>> echo "${XX/*
>>
>> }"
>>
> Hello,
>
> Yes, that does seem to work :-)
>
> Although I have to admit I'm not sure why! I'll investigate further :-)
Basically it just drops the longest substring that matches the given
pattern (match anything followed by two newlines). This does
potentially miss some edge cases if you can have strings containing
only a single leading or possibly trailing blank line. But you can
remove leading and trailing blank lines if necessary or come up with
something more clever. See the "Parameter Expansion" section of the
bash man page for the details of this and other frequently useful ways
to expand/modify variables.
John
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Re: Bash - an odd problem using sed or awk or for
On Thu, 2012-11-29 at 18:56 -0600, inode0 wrote:
>
> Oh, for a simple variable this should work
>
> echo "${XX/*
>
> }"
>
Hello,
Yes, that does seem to work :-)
Although I have to admit I'm not sure why! I'll investigate further :-)
Many thanks,
John.
--
John Horne Tel: +44 (0)1752 587287
Plymouth University, UK Fax: +44 (0)1752 587001
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Re: Bash - an odd problem using sed or awk or for
On 11/29/2012 04:33 PM, John Horne wrote: Hello, I have a bash script in which a variable is set to one or more lines of text. What I want is to remove any lines up to and including a blank line (or alternatively to echo all the lines after the last blank line). There may be zero or more blank lines, and the blank lines need not be consecutive. If there is no blank line, then all the lines should be shown. If the last line is blank, then nothing should be shown. So for example the variable may contain: (the '=' are not part of the variable) abc def hijk xyz So in this case what is wanted is: hijk xyz to be shown. I tried something like: echo "$XX" | sed -e '/./,/^$/d' but this didn't display anything. (Where XX is the variable.) I also tried using a 'for' loop but again this displayed nothing: opt="" IFS=$'\n' for n in $XX; do test -z "$n" && opt="" || opt="$opt $n"; done (Echoing $opt after this shows that it contains nothing.) I'm not sure why but even using a for loop just to show it had seen a blank line didn't work either (using something like 'test -z "$n" && echo found'). My understanding was that by setting IFS to a newline, then the 'for' loop should see the blank line and just set '$n' to the null string. We should then be able to test on that. Ideally what I am looking for is a snappy one line 'sed' or 'awk' command to handle this :-) Unfortunately at the moment I seem to be getting nowhere though, even with the 'for' loop. Thanks, John. John, this is easily accomplished, but you are not telling us where and from what source is your variable being set. For example, are you reading the lines in from a file or from stdin? If so, then I would get rid of lines containing any space(s) as follows: while read line; do set $line [ $# -lt 2 ] && echo $line done < SomeFile If reading from stdin, then you only need done (without the < SomeFile). It will print only the lines that lack a space. -- users mailing list users@lists.fedoraproject.org To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org
Re: Bash - an odd problem using sed or awk or for
On Thu, Nov 29, 2012 at 6:48 PM, inode0 wrote:
> On Thu, Nov 29, 2012 at 5:33 PM, John Horne wrote:
>> Hello,
>>
>> I have a bash script in which a variable is set to one or more lines of
>> text. What I want is to remove any lines up to and including a blank
>> line (or alternatively to echo all the lines after the last blank line).
>> There may be zero or more blank lines, and the blank lines need not be
>> consecutive. If there is no blank line, then all the lines should be
>> shown. If the last line is blank, then nothing should be shown. So for
>> example the variable may contain:
>>
>> (the '=' are not part of the variable)
>> abc def
>>
>> hijk
>> xyz
>>
>>
>> So in this case what is wanted is:
>>
>>
>> hijk
>> xyz
>>
>>
>> to be shown.
>>
>> I tried something like:
>>
>>echo "$XX" | sed -e '/./,/^$/d'
>>
>> but this didn't display anything. (Where XX is the variable.)
>
> echo "${XX[*]/*
>
> }"
Oh, for a simple variable this should work
echo "${XX/*
}"
John
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Re: Bash - an odd problem using sed or awk or for
On Thu, Nov 29, 2012 at 5:33 PM, John Horne wrote:
> Hello,
>
> I have a bash script in which a variable is set to one or more lines of
> text. What I want is to remove any lines up to and including a blank
> line (or alternatively to echo all the lines after the last blank line).
> There may be zero or more blank lines, and the blank lines need not be
> consecutive. If there is no blank line, then all the lines should be
> shown. If the last line is blank, then nothing should be shown. So for
> example the variable may contain:
>
> (the '=' are not part of the variable)
> abc def
>
> hijk
> xyz
>
>
> So in this case what is wanted is:
>
>
> hijk
> xyz
>
>
> to be shown.
>
> I tried something like:
>
>echo "$XX" | sed -e '/./,/^$/d'
>
> but this didn't display anything. (Where XX is the variable.)
echo "${XX[*]/*
}"
John
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Re: Bash - an odd problem using sed or awk or for
On Thu, 2012-11-29 at 23:33 +, John Horne wrote: > Hello, > > I have a bash script in which a variable is set to one or more lines of > text. What I want is to remove any lines up to and including a blank > line (or alternatively to echo all the lines after the last blank line). > There may be zero or more blank lines, and the blank lines need not be > consecutive. If there is no blank line, then all the lines should be > shown. If the last line is blank, then nothing should be shown. So for > example the variable may contain: > > (the '=' are not part of the variable) > abc def > > hijk > xyz > > > So in this case what is wanted is: > > > hijk > xyz > > > to be shown. > > I tried something like: > >echo "$XX" | sed -e '/./,/^$/d' > > but this didn't display anything. (Where XX is the variable.) > I also tried using a 'for' loop but again this displayed nothing: > >opt="" >IFS=$'\n' >for n in $XX; do test -z "$n" && opt="" || opt="$opt $n"; done > > (Echoing $opt after this shows that it contains nothing.) I'm not sure > why but even using a for loop just to show it had seen a blank line > didn't work either (using something like 'test -z "$n" && echo found'). > My understanding was that by setting IFS to a newline, then the 'for' > loop should see the blank line and just set '$n' to the null string. We > should then be able to test on that. > > Ideally what I am looking for is a snappy one line 'sed' or 'awk' > command to handle this :-) Unfortunately at the moment I seem to be > getting nowhere though, even with the 'for' loop. echo $FOO | grep . poc -- users mailing list users@lists.fedoraproject.org To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org
