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Use parameter expansion over a parameter expansion in bash.


 
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# 1  
Old 01-28-2020
Use parameter expansion over a parameter expansion in bash.

Hello All,

Could you please do help me here as I would like to perform parameter expansion in shell over a parameter expansion.

Let's say I have following variable.
Code:
path="/var/talend/nat/cdc"

Now to get only nat I could do following.
Code:
path1="${path%/*}"
path1="${path1##*/}"

Here in this approach I am creating a temporary variable path1 and again performing parameter expansion, how about if I want to perform this in single time without having temporary variable? I have tried it like:

Code:
echo "${((${path%/*}))##*/}"

Which is giving me an error. Any help, guidance is appreciated.

Thanks,
R. Singh
This User Gave Thanks to RavinderSingh13 For This Post:
# 2  
Old 01-28-2020
Hi
try this
Code:
basename $(dirname /var/talend/nat/cdc)

--- Post updated at 11:33 ---

Code:
basename ${path%/*}

--- Post updated at 11:51 ---

Here is a solution I finded completely not practical but interesting
Code:
: ${path%/*}; echo ${_##*/}

This User Gave Thanks to nezabudka For This Post:
# 3  
Old 01-28-2020
love things like that
Code:
echo $(expr match "$path" '.*/\([^/]*\)/[^/]*')


Last edited by nezabudka; 01-28-2020 at 06:46 AM..
This User Gave Thanks to nezabudka For This Post:
# 4  
Old 01-28-2020
Hi Ravinder...

A fun approach but fully 'dash' compliant:
Code:
Last login: Tue Jan 28 14:17:35 on ttys000
AMIGA:amiga~> dash
AMIGA:\u\w> path="/var/talend/nat/cdc"
AMIGA:\u\w> path=${path%/*};path=${path##*/}
AMIGA:\u\w> printf "%s\n" "${path}"     
nat
AMIGA:\u\w> exit
AMIGA:amiga~> _

These 2 Users Gave Thanks to wisecracker For This Post:
# 5  
Old 01-28-2020
Hi @wisecracker
I think this is the same option. Change a little and it will be quite practical
Code:
: ${path%/*} && echo ${_##*/}

but it's just not convenient to pass this parameter on

Last edited by nezabudka; 01-28-2020 at 12:01 PM..
This User Gave Thanks to nezabudka For This Post:
# 6  
Old 01-28-2020
Hi nez...
I do not like 'eval' but here goes and is also 'dash' compliant...
Code:
Last login: Tue Jan 28 14:17:35 on ttys000
AMIGA:amiga~> dash
AMIGA:\u\w> path="/var/talend/nat/cdc"
AMIGA:\u\w> path=$( eval path=${path%/*} && echo ${_##*/} )
AMIGA:\u\w> echo "${path}"
nat
AMIGA:\u\w> exit
AMIGA:amiga~> _

# 7  
Old 01-28-2020
This is how it will be without "eval"
Code:
$( : ${path%/*} && echo ${_##*/} )

that would be without "echo" Smilie
This User Gave Thanks to nezabudka For This Post:

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