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I have bash script which modified file like this
sed -i "/hello world/d" /etc/postfix/virtual
and I ran this script from web application. sed command create temporary file in that directory but user under which web application works doesn't have permissions to create files in that directory. I do not want to give more permissions for the user to that folder. Is it possible to specify temp file location for sed command?
I am new in linux so sorry if my question is too easy but I didn't find any solution.
Thanks!
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sed creates residue temp files with the -i flag.
In Unix/Linux shell we can use the mktemp commmand to create a temporary directory inside the /tmp directory. The -d flag instructs the command to create the directory. The -t flag allows us to provide a template. Each X character will be replaced by a random character.
Open your File Explorer (it's usually the first button on your desktop taskbar, looks like a folder). Go to the "This PC" section on the left, and then double-click your C: drive. On the Home tab at the top, click "New Folder" and name it "Temp".
In Unix and Linux, the global temporary directories are /tmp and /var/tmp. Web browsers periodically write data to the tmp directory during page views and downloads. Typically, /var/tmp is for persistent files (as it may be preserved over reboots), and /tmp is for more temporary files.
Sed works by processing the input file one line at a time. On each line, the substitute ( s) command will replace the first occurrence of the text between the first two slashes ( /<YEAR>/) by the text between the last two ones ( /2018/ ). Think of that like the search-replace feature you have in a GUI text editor.
Replacing or substituting string : Sed command is mostly used to replace the text in a file. The below simple sed command replaces the word “unix” with “linux” in the file. $sed 's/unix/linux/' geekfile.txt Output : linux is great os. unix is opensource.
Most Linux distributions provide the convenient mktemp utility, which permits us to effortlessly create a temporary file in Linux. Running mktemp with no arguments will create a temporary file in /tmp and show the file’s path in the terminal’s output: 3.2. Using Templates
The p means “print matched lines.” By default, sed prints all lines. We’d see all the text in the file with the matching lines printed twice. To prevent this, we’ll use the -n (quiet) option to suppress the unmatched text.
The file must be modified via temporary file, this is actually what sed was doing but it lacked permissions.
When dealing with such a situation, we just do this process manually.
## TEMP File
TFILE=`mktemp --tmpdir tfile.XXXXX`
trap "rm -f $TFILE" 0 1 2 3 15
##
sed 's_XXX_YYY_' /etc/example > "$TFILE"
cat "$TFILE" > /etc/example
## trap Deletes TFILE on Exit
You could use "sponge" from moreutils.
sed "/hello world/d" /etc/postfix/virtual | sponge /etc/postfix/virtual
Old question, but I was surprised to find nobody suggesting to use some good-ol' RAM via a variable. Here's what I ended up doing, no need for a temp file at all:
TEMP_SED=$(sed "/hello world/d" /etc/postfix/virtual)
echo "$TEMP_SED" > /etc/postfix/virtual
unset TEMP_SED
Note the quotes around the variable when echoing. This is needed to preserve any newlines in the file.
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