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how do you take one word from a file and change it to an absolute path? Basically I need to take one word from a unix file and change it to a absolute directory path in that file. The file name is httpd.conf. The path for that file is /home/Tina/apache/conf/httpd.conf. The line is ServerRoot "/usr". The "/usr" is what i need to change to /home/Tina/apache.

Tina@Irv-PC ~/apache/conf
$ cat httpd.conf
#
# This is the main Apache HTTP server configuration file. It contains the
# configuration directives that give the server its instructions.

# Do not add a slash at the end of the directory path.
#
ServerRoot "/usr"

#
# DocumentRoot: The directory out of which you will serve your documents.
#
DocumentRoot "/Library/WebServer/Documents"
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    Please edit your question to include a before and after example: as it is, it is not clear what you are asking. Commented Mar 17, 2015 at 17:19
  • ok the before line of the file is not a comment line and it says ServerRoot "/usr and i need to change the /usr to an absolute directory path Commented Mar 17, 2015 at 17:23
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    Tina, If you want helpful answers, please do as @jasonwryan suggests: edit your question (because, unlike a comment, the question text can be formatted accurately) to include a short before and after example (examples are critical because word descriptions often lack key details). Commented Mar 17, 2015 at 17:36
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    Yes, please do as the others have suggested. For one thing, that will help us understand your terms since both /usr and /home/Tina/apache/conf/httpd.conf are absolute paths. Commented Mar 17, 2015 at 18:35

2 Answers 2

Reset to default
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Try this:

$ sed -i.orig '/ServerRoot/s_"/usr"_/home/Tina/apache_' /home/Tina/apache/conf/httpd.conf

If you want to put double quotes around /home/Tina/apache:

$ sed -i.orig '/ServerRoot/s_"/usr"_"/home/Tina/apache"_' /home/Tina/apache/conf/httpd.conf

Here at first we matched if the line contains "ServerRoot" (/ServerRoot/), if yes then we have made the required substitution (s_"/usr"_"/home/Tina/apache"_). As you have / in the path, we have used _ as the sed substitution delimiters. The modified file will be /home/Tina/apache/conf/httpd.conf and the original file will be kept as /home/Tina/apache/conf/httpd.conf.orig.

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To avoid side effects, I'd replace the whole line:

sed -i.bak -e 's#^ *ServerRoot  *"/usr" *$#ServerRoot "/home/Tina/apache"#' httpd.conf

It is customary to use 's/from/to/', but since you have slashes everywhere, it's wise to use another character so you don't have to write \/ for every path seperator slash in your expression. I put ^...$ around your from-expression to make sure to match only lines consisting of exactly that (^ is beginning of line, $ end of line)

The -i switch will edit your file in place, but make a backup to httpd.conf.bak, which is a very good idea when editing system config files.

In case your sed doesn't support alternate delimiters, you could try

sed -i.bak -e 's/^ *ServerRoot  *"\/usr" *$/ServerRoot "\/home\/Tina\/apache"/' httpd.conf
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  • Ok. Thanks for your prompt reply. I am not getting an error, but it is not making the change either. Commented Mar 17, 2015 at 18:05
  • Hm. Any spaces in the line you want to replace? As originally written, ServerRoot must not be indented, nor may there be more than exactly one space between ServerRoot and "...", nor may there be space or comments after the path. I'll update my answer to allow more spaces in a second. Commented Mar 17, 2015 at 18:28
  • so sorry but it still does the same, no error but no change in the file syntax either Commented Mar 17, 2015 at 18:28
  • no extra spaces Commented Mar 17, 2015 at 18:32
  • I can't help but think that I am over thinking this. Basically, it should be a simply replacement of "/usr" with "/home/Tina/apache". Commented Mar 17, 2015 at 18:42

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