sed in-place flag that works both on Mac (BSD) and Linux

Question

Is there an invocation of sed todo in-place editing without backups that works both on Linux and Mac? While the BSD sed shipped with OS X seems to

Answer 1

If you need to do sed in-place in a bash script, and you do NOT want the in-place to result with .bkp files, and you have a way to detect the os (say, using ostype.sh), -- then the following hack with the bash shell built-in eval should work:

OSTYPE="$(bash ostype.sh)"

cat > myfile.txt <<"EOF"
1111
2222
EOF

if [ "$OSTYPE" == "osx" ]; then
  ISED='-i ""'
else # $OSTYPE == linux64
  ISED='-i""'
fi

eval sed $ISED 's/2222/bbbb/g' myfile.txt
ls 
# GNU and OSX: still only myfile.txt there

cat myfile.txt
# GNU and OSX: both print:
# 1111
# bbbb

# NOTE: 
# if you just use `sed $ISED 's/2222/bbbb/g' myfile.txt` without `eval`,
# then you will get a backup file with quotations in the file name, 
# - that is, `myfile.txt""`

Answer 2

The following works for me on Linux and OS X:

sed -i' ' <expr> <file>

e.g. for a file f containing aaabbaaba

sed -i' ' 's/b/c/g' f

yields aaaccaaca on both Linux and Mac. Note there is a quoted string containing a space, with no space between the -i and the string. Single or double quotes both work.

On Linux I am using bash version 4.3.11 under Ubuntu 14.04.4 and on the Mac version 3.2.57 under OS X 10.11.4 El Capitan (Darwin 15.4.0).

Answer 3

There is no way to have it working.

One way is to use a temporary file like:

TMP_FILE=`mktemp /tmp/config.XXXXXXXXXX`
sed -e "s/abc/def/" some/file > $TMP_FILE
mv $TMP_FILE some/file

This works on both

Answer 4

If you really want to just use sed -i the 'easy' way, the following DOES work on both GNU and BSD/Mac sed:

sed -i.bak 's/foo/bar/' filename

Note the lack of space and the dot.

Proof:

# GNU sed
% sed --version | head -1
GNU sed version 4.2.1
% echo 'foo' > file
% sed -i.bak 's/foo/bar/' ./file
% ls
file  file.bak
% cat ./file
bar

# BSD sed
% sed --version 2>&1 | head -1
sed: illegal option -- -
% echo 'foo' > file
% sed -i.bak 's/foo/bar/' ./file
% ls
file  file.bak
% cat ./file
bar

Obviously you could then just delete the .bak files.

Answer 5

When on OSX, I always install GNU sed version via Homebrew, to avoid problems in scripts, because most scripts were written for GNU sed versions.

brew install gnu-sed --with-default-names

Then your BSD sed will be replaced by GNU sed.

Alternatively, you can install without default-names, but then:

• Change your PATH as instructed after installing gnu-sed
• Do check in your scripts to chose between gsed or sed depending on your system

Answer 6

Steve Powell's answer is quite correct, consulting the MAN page for sed on OSX and Linux (Ubuntu 12.04) highlights the in-compatibility within 'in-place' sed usage across the two operating systems.

JFYI, there should be no space between the -i and any quotes (which denote an empty file extension) using the Linux version of sed, thus

sed Linux Man Page

#Linux
sed -i"" 

and

sed OSX Man page

#OSX (notice the space after the '-i' argument)
sed -i "" 

I got round this in a script by using an alias'd command and the OS-name output of 'uname' within a bash 'if'. Trying to store OS-dependant command strings in variables was hit and miss when interpreting the quotes. The use of 'shopt -s expand_aliases' is necessary in order to expand/use the aliases defined within your script. shopt's usage is dealt with here.