How to substitute environment variable in SED Stack Overflow?

How to substitute environment variable in SED Stack Overflow?

Let’s say the current directory is /home/yourname in this case, your command below: which is not valid. You need to put a \\ character in front of each / in your $PWD if you want to do this. you can not known what character will occur in $PWD, / : OR @. the good way is replace (escape) the special character in $PWD.

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 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 substitute Foo in SED Stack Overflow?

So if you want to search for ‘foo’ and replace it with the content of $BAR, you can enclose the sed command in double-quotes. In the first, $BAR will not expand correctly while in the second $BAR will expand correctly. Another easy alternative:

How to replace a placeholder in a text file in Bash?

Since the substitution is between “, ” $ (cat template.txt) ” becomes the output of cat template.txt. where i and word are the specified environment variables. The following bash function should only replace $ {var1} syntax and ignore other shell special chars such as `backticks` or $var2 or “double quotes”.

How to replace a variable in a template file?

I want to pipe the output of a “template” file into MySQL, the file having variables like $ {dbName} interspersed. What is the command line utility to replace these instances and dump the output to standard output? Sed! Thanks to Jonathan Leffler for the tip to pass multiple -e arguments to the same sed invocation.

When to use a variable substitution in shell?

Variable substitution enables the shell programmer to manipulate the value of a variable based on its state. If var is null or unset, word is substituted for var. The value of var does not change. If var is null or unset, var is set to the value of word. If var is null or unset, message is printed to standard error.

How to use a substitution in a SED file?

We first get the current date and time from a command substitution and save it in a variable MY_DATE. After we get the date, we fill it in the file by using a sed substitution. We’ve used the GNU sed command’s -i option to do an in-place edit. Let’s execute our script and check if it works as we expect:

Which is an example of a command substitution?

When performing the command substitution make sure that you use the backquote, not the single quote character. Command substitution is generally used to assign the output of a command to a variable. Each of the following examples demonstrates the command substitution −

How to replace a path with another path in SED?

sed can use any separator instead of / in the s command. Just use something that is not encountered in your paths: and so on. Alternatively (and if you don’t want to guess), you can pre-process your path with sed to escape the slashes: and then do what you need with $pwdesc.

How to replace a path in a file with a new path?

I am using sed to replace a path in a file with new path. What is missing or not right here? I get > with it. You are with the backtick ( `) opening a subshell statement which you are never terminating. Make sure your quotes match.

How to replace insthome with value in SED?

We want to replace all the appearance of INSTHOME with the value we hold in $HOME. Here is what I do initially: g stands for “global”, which means to do this find & replace for the whole line. If you leave off the g and INSTHOME appears twice on the same line, only the first INSTHOME is changed to $HOME

How to replace a string with quote in SED?

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): sed -i “s/quote me/\\”&\\”/” “$file”.

How to substitute old line for new line in SED?

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.

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:

Do you need to interpolate strings in SED?

Other Unix platforms (e.g. AIX, HP-UX, Solaris) may have variants of sed that do not support -i at all. It is not required by the POSIX specification for sed. You must use ” ‘s so that the $line and $new_line are interpolated. Also use | or any character not found in the match or replacement strings as a delimiter.

Which is the delimiter for Stack Overflow in SED?

If your text can contain almost any plain text character, use a control character (e.g. control-A or control-G) as the delimiter. Note that the use of -i here mirrors what is in the question, but that assumes the use of GNU sed. BSD sed (found on Mac OS X too) requires a suffix.

Is there a way to replace in situ with SED?

You can use sed -i ” … to replace in situ; that does not work with GNU sed. To be portable between the two, use -i.bak; that will work with both — but gives you a backup file that you’ll probably want to delete. Other Unix platforms (e.g. AIX, HP-UX, Solaris) may have variants of sed that do not support -i at all.