Dear friends,

I have the following problem with many curly braces.
In some file I have many patterns like this: {\{}}
I want to get rid of all of them

My question is: how can I do this with sed?
What is the correct regular expression, that matches this pattern?

I tried the following

sed -e 's/{\{}}//g' ... does no work
sed -e 's/{\\\{}}//g' ... does not work
sed -e 's/\{\\\{\}\}//g' ... does not work


So, how to do this?


Thanks.

TryDifferent separator char is generally a good idea.

For regular sed, only the backslash is a meta-character, and needs to be escaped.
sed 's/{\\{}}//g' file >modified-file

If you enable extended regular expressions then the { and } characters are meta-characters and need to be escaped as well.
sed -r 's/\{\\\{\}\}//g' file >modified-file

thank you very much

I still do not understand something about these regular expressions
with meta-characters.

Here is another problem:

how to transform

\text\{eps\} into \epsilon


I tried

sed -r -e "s/\\\text\\\{eps\\\}/\\\epsilon/g"

and

sed -r -e "s:\\\text\\\{eps\\\}:\\\epsilon:g"

but it does not work. What is wrong?

In the context of sed "\" has a special meaning and therefor must be escaped (with "\"--which makes it a bit confusing.) to be taken literally.
In context, however, "{" or "}" do not have special meaning and therefor do not need to be escaped. If you turn on extended Regexes, then they DO need to be escaped....

To replace "\text\" with text:

sed 's_\\text\\_text_g'**

To replace "{eps}" with "eps":

sed 's_{eps}_eps_g'
OR:
sed -r 's_\{eps\}_eps_g'

Any character which has a special meaning--in the context in which it used--must be escaped if it is to be taken literally.

In some cases, escaping is used to give special meaning when the character would other wise be taken literally.

Escaping an escape means that it is no longer an escape--thus you cannot use another escape to nullify the first escape. e.g. "\\\x" means literal "\", followed by an escaped "x". "\\\\" means 2 literal "\"s

say the above 5 times fast.....


**Remember that the first character after s is always the delimiter. Use any character you want to make it readable and to avoid ambiguity.

Yes, I knew that, but I still do not understand what to do
if \ and { are next to each other in the pattern.

You may have misunderstood me.

I know how to replace {eps} with eps,
but to replace \{eps\} with eps is a different story
now I have both "\" and "{" next to each other and the first
makes it difficult to escape the second


sed -r "s/\\{eps\\}/eps/g"

or

sed -r "s/\\\{eps\\\}/eps/g"


do not work

First--I did a major boo-boo earlier---to use extended regexes, its sed -r, not -e.

in basic regexes, you don't need to escape the "{" or "}"

To replace "\{eps\}":
Basic:

sed 's_\\{eps\\}_newtext_g' (no -r)


Extended:

sed -r 's_\\\{eps\\\}_newtext_g'

This works on my system---what exactly happens when you try it?

thank you.


It works.
It is interesting that it did not work
with / and : separators, it works with _ only.


Thanks again.



but what if one needs to replace \{phi0\} with phi_0 ?

Even with the "s" omitted? (yes, I screwed up again....)


Both of these work on my system:

sed 's/\\{eps\\}/newtext/g'

sed 's:\\{eps\\}:newtext:g'


For the truly obsessive, here's a good one:

sed 's\text\newtext\g' works...... Now, having used "\" for the delimiter, how would you escape something??

Hi.
It worked for me using single quotes (and correcting the syntax):
Best wishes ... cheers, makyo

I hope you don't make a habit of using a backslash for a delimiter. It is the character used to escape other characters. You are confusing yourself with a contrived example.