Removing substring from string variable in bash

Question

I have a bash string variable:

switches="-r cc -c 1,2,3,4 -u"

where numbers 1,2,3,4 can be any integer, like:

-c 25,45,78,34.

Moreover, it can be with fewer numbers, like:

-c 1

-c 1,2

or

-c 1,2,3,4

It can't be like: -c 1,2,3

So -c can have one, two, or four integers only.

I forgot to mention that that this pattern can appeares also at the beginning, or at the end of the string variable $switches too, like:

-r cc -u -c 1,2,3,4

-r cc -u -c 1,2,3

And one more thing: this pattern can be appeared in the $switches variable only once.

How can I remove the '-c 1,2,3,4 ' part of switches variable using just bash? I tried with this:

switches=${switches/ -c /}

but get this:

-r cc1,2,3,4 -u

I expect this:

-r cc -u

Best, Pal

You are already doing it wrong in the first line. switches should be an array, not a regular variable: switches=(-r cc -c 1,2,3,4 -u). — chepner
– chepner, Commented Jan 21, 2018 at 0:00
The switches array could have more then those three values: (-r cc), (-c 1,2,3,4), (-u). switches array can have maximum 17 string values. — Pal Csanyi
– Pal Csanyi, Commented Jan 21, 2018 at 6:13
The switches array could have more then those three values: (-r cc), (-c 1,2,3,4), (-u). switches array can have maximum 17 string values. (-r cc) is one value in the array, (-c 1,2,3,4) or (-c 1) or (-c 1,2) is another value, (-u) is another value, (-g) is another, and so on. In this case switches=(-r cc -c 1,2,3,4 -u) is not the proper way for creating the switches array, right? — Pal Csanyi
– Pal Csanyi, Commented Jan 21, 2018 at 6:20
Then it should be created like this: switches=('-r cc' '-c 1,2,3,4' '-u' '-g'). But then how can I remove a value of that array, because value '-c 1,2,3,4' cod vary like this: '-c 1' '-c 1,2' '-c 1,2,3,4' ? — Pal Csanyi
– Pal Csanyi, Commented Jan 21, 2018 at 7:01
OK, I can arrange so so in switches array every values goes in to right place, like this: switches=('-r cc' '-l l' '-c 1,2,3,4' '-g' '-e none' '-f 15' '-o 5' '-u' '-t 50' '-s 0' '-S 200' '-a 0' '-p 0' '-T' '-b white' '-F 10' '-i 1') so eg. '-t 50' could have always the index number of 8. So how can then remove such a value from the switches array? — Pal Csanyi
– Pal Csanyi, Commented Jan 21, 2018 at 7:33

PesaThe · Accepted Answer · 2018-01-20 20:50:26Z

1

Using extglob:

shopt -s extglob                         # enables extended globbing
switches=${switches//-c *([^ ])}

*([^ ]): matches any number of non-spaces

This will leave you with unnecessary spaces. More complicated solution:

switches=${switches//-c *([^ ])*( )}
switches=${switches/%*( )}

*([^ ])*( ): matches any number of non-spaces and any number of spaces after
${switches/%*( )}: if the last option is also -c, the code above wouldn't remove the spaces left by it. /%*( ) removes any number of spaces from the end

edited Jan 20, 2018 at 20:50

answered Jan 20, 2018 at 20:26

PesaThe

7,5691 gold badge23 silver badges47 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Pal Csanyi Over a year ago

This code did it: switches=${switches//-c *([^ ])*( )}. Thank you very much!

Collectives™ on Stack Overflow

Removing substring from string variable in bash

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related