CODEWITHSUNDEEP
bash
Equation Solver
Equation Solver

Reputation: 553

How truncate the ../ characters from string in bash?

How can I truncate the ../ or .. characters from string in bash So, If I have strings

str1=../lib
str2=/home/user/../dir1/../dir2/../dir3

then how I can get string without any .. characters in a string like after truncated result should be

str1=lib
str2=/home/user/dir1/dir2/dir3

Please note that I am not interesting in absolute path of string.

Upvotes: 0

Views: 560

Answers (3)

paxdiablo
paxdiablo

Reputation: 881633

You could use:

pax> str3=$(echo $str2 | sed 's?\.\./??g') ; echo $str3
/home/user/dir1/dir2/dir3

Just be aware (as you seem to be) that's a different path to the one you started with.

If you're going to be doing this infrequently, forking an external process to do it is fine. If you want to use it many times per second, such as in a tight loop, the internal bash commands will be quicker:

pax> str3=${str2//..\/} ; echo $str3
/home/user/dir1/dir2/dir3

This uses bash pattern substitution as described in the man page (modified slightly to adapt to the question at hand):

${parameter/pattern/string}

The parameter is expanded and the longest match of pattern against its value is replaced with string. If pattern begins with /, all matches of pattern are replaced with string.

If string is null, matches of pattern are deleted and the / following pattern may be omitted.

Upvotes: 1

jaypal singh
jaypal singh

Reputation: 77105

You don't really need to fork a sub-shell to call sed. Use bash parameter expansion: 

echo ${var//..\/}


str1=../lib
str2=/home/user/../dir1/../dir2/../dir3


echo ${str1//..\/}     # Outputs lib
echo ${str2//..\/}     # Outputs /home/user/dir1/dir2/dir3

Upvotes: 3

Raghuram
Raghuram

Reputation: 3967

You can use sed to achieve it

sed 's/\.\.\///g'

For example

echo $str2 | sed 's/\.\.\///g'

OP => /home/user/dir1/dir2/dir3

Upvotes: 0

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