How to specify beginning-of-line/end-of-line characters inside a regex range


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# 1  
How to specify beginning-of-line/end-of-line characters inside a regex range

How can I specify special meaning characters like ^ or $ inside a regex range. e.g

Suppose I want to search for a string that either starts with '|' character or begins with start-of-line character.

I tried the following but it does not work:

Code:
sed 's/\([|^]\)/<do something here>/g' file1

It is obviously interpreting ^ as the literal caret character. Any way out?
# 2  
This works on solaris using ksh93:

Code:
$ cat x.dat
kldfhvlkjsdhv
;aslkflksdfj
sadfkjlskdjf
gcw|test123
gcw^test456
;lksdkhdsf
;lkhaddhb
hdashdkj
$ sed 's/[|^]test/found_it/' x.dat
kldfhvlkjsdhv
;aslkflksdfj
sadfkjlskdjf
gcwfound_it123
gcwfound_it456
;lksdkhdsf
;lkhaddhb
hdashdkj
$

# 3  
I don't think I made myself clear. Let me give an example. Suppose the file I have is:

Code:
testABCD
jklmn|testDEFGH
klmnoptestABCD

I want the sed command to replace only the first two instances of the string "test" with "found_it", i.e. the output should contain:

Code:
found_itABCD
jklmn|found_itDEFGH
klmnoptestABCD

i.e. the string test should only be replaced with found_it if it occurs after a pipe or at the beginning of the line. I suppose this can be achieved with :

Code:
sed -e 's/^test/found_it/g' -e 's/|test/found_it/g' file1

but shouldn't this be achievable using regex patterns too?
# 4  
I believe some versions of sed allow a logical or. Mine does not. Try this:

Code:
sed 's/^test\||test/found_it/g' filename

If portability is a concern, you might want to stick with something like this:
Code:
sed 's/|test/FOUND/g;s/^test/FOUND/g' filename

 

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