How to use sed to replace specific line with a?

How to use sed to replace specific line with a?

I have a variable called line=1 and a variable string substitute=hello1. I want to replace the string in the line described by the variable line with my new string variable called substitute. How would I use sed to do this? Or awk? If thats what you are in to, as long as I can input variables that I can change in a while loop.

How do I use variables in a sed command?

We can use variables in sed using double quotes: If you have a slash / in the variable then use different separator, like below: Highly active question. Earn 10 reputation (not counting the association bonus) in order to answer this question. The reputation requirement helps protect this question from spam and non-answer activity.

Why do I have to substitute my Date in SED?

As the output above shows, the line with “ CURRENT_TIME = ” has been substituted. However, instead of the current date and time, the literal “ $MY_DATE ” is filled. This happened because we used single quotes in our sed command. Shell variables will not get expanded within single quotes.

How to replace a pattern in Bash using SED?

$ {parameter/pattern/string} — replace the first match of pattern with string. $ {parameter//pattern/string} — replace all matches of pattern with string. website=$ {website // / / \\\\/} ^ ^ ^ ^ | | | | | | | string, ‘\\’ needs to be backslashed | | delimiter | pattern replace globally

How to pass the SED code in Bash?

We use a heredoc to pass the sed code. The sed code is reading a file and placing jts contents on the stdout and suppressing the original line by virtue of the -n option. $substitute is not equal to a single period (.) end the change with .

When to use quote in a sed command?

When you require the quote character in the replacement string, you have to precede it with a backslash which will be interpreted by the shell. In the following example, the string quote me will be replaced by “quote me” (the character & is interpreted by sed):

How to replace old line variable with new line variable?

The contents of this variable looks like this: I have created a second variable called new_line that is similar to old_line but with some modifications in the text. I want to substitute the contents of old_line with the contents of new_line using sed. So far I have the following, but it doesn’t work:

How to substitute old line with new line?

I want to substitute the contents of old_line with the contents of new_line using sed. So far I have the following, but it doesn’t work: Since $ {old_line} contains many regex special metacharacters like *, ? etc therefore your sed is failing.

How to find the value of a variable in SED?

Note that your original version contains single quotes around the sed string, which doesn’t insert the value of $line. It is trying to look for the literal line after the end of the line $ (which will never find anything). Since you are looking for the value of the variable in $line, you need to do an eval to get this.

How to search and replace variables in a file?

But I need to modify only the variables which are present in variable_list file and leave others as it is. The first sed expression escapes the $ which is a regex metacharacter. The second extracts just the variable name, then we use indirection to get the value in our current shell and use it in the sed expression.

How can I use sed to read from standard input?

However you could cobble something together using sed -f – to read commands from standard input, together with your shell. For example: If the line number matches either 1, 10, or 100, branch to label 1; on other lines, just branch to the end (which, by default, prints the line).

Can a SED address consist of more than one line?

As far as I know, sed addresses may only consist of a single line, or a range of lines. However you could cobble something together using sed -f – to read commands from standard input, together with your shell. For example:

How to replace a line with a number?

The following examples demonstrate the removing or changing of text by specific line numbers: # replace line 17 with some replacement text and make changes in file (-i switch) # the “-i” switch indicates that we want to change the file.