How to remove trailing whitespaces with sed? - sed

Question

I have a simple shell script that removes trailing whitespace from a file. Is there any way to make this script more compact (without creating a temporary file)?
sed 's/[ \t]*$//' $1 > $1__.tmp
cat $1__.tmp > $1
rm $1__.tmp

Answer 1

You can use the in place option -i of sed for Linux and Unix:
sed -i 's/[ \t]*$//' "$1"
Be aware the expression will delete trailing t's on OSX (you can use gsed to avoid this problem). It may delete them on BSD too.
If you don't have gsed, here is the correct (but hard-to-read) sed syntax on OSX:
sed -i '' -E 's/[ '$'\t'']+$//' "$1"
Three single-quoted strings ultimately become concatenated into a single argument/expression. There is no concatenation operator in bash, you just place strings one after the other with no space in between.
The $'\t' resolves as a literal tab-character in bash (using ANSI-C quoting), so the tab is correctly concatenated into the expression.

Answer 2

At least on Mountain Lion, Viktor's answer will also remove the character 't' when it is at the end of a line. The following fixes that issue:
sed -i '' -e's/[[:space:]]*$//' "$1"

Answer 3

Thanks to codaddict for suggesting the -i option.
The following command solves the problem on Snow Leopard
sed -i '' -e's/[ \t]*$//' "$1"

Answer 4

It is best to also quote $1:
sed -i.bak 's/[[:blank:]]*$//' "$1"

Answer 5

var1="\t\t Test String trimming "
echo $var1
Var2=$(echo "${var1}" | sed 's/^[[:space:]]*//;s/[[:space:]]*$//')
echo $Var2

Answer 6

I have a script in my .bashrc that works under OSX and Linux (bash only !)
function trim_trailing_space() {
if [[ $# -eq 0 ]]; then
echo "$FUNCNAME will trim (in place) trailing spaces in the given file (remove unwanted spaces at end of lines)"
echo "Usage :"
echo "$FUNCNAME file"
return
fi
local file=$1
unamestr=$(uname)
if [[ $unamestr == 'Darwin' ]]; then
#specific case for Mac OSX
sed -E -i '' 's/[[:space:]]*$//' $file
else
sed -i 's/[[:space:]]*$//' $file
fi
}
to which I add:
SRC_FILES_EXTENSIONS="js|ts|cpp|c|h|hpp|php|py|sh|cs|sql|json|ini|xml|conf"
function find_source_files() {
if [[ $# -eq 0 ]]; then
echo "$FUNCNAME will list sources files (having extensions $SRC_FILES_EXTENSIONS)"
echo "Usage :"
echo "$FUNCNAME folder"
return
fi
local folder=$1
unamestr=$(uname)
if [[ $unamestr == 'Darwin' ]]; then
#specific case for Mac OSX
find -E $folder -iregex '.*\.('$SRC_FILES_EXTENSIONS')'
else
#Rhahhh, lovely
local extensions_escaped=$(echo $SRC_FILES_EXTENSIONS | sed s/\|/\\\\\|/g)
#echo "extensions_escaped:$extensions_escaped"
find $folder -iregex '.*\.\('$extensions_escaped'\)$'
fi
}
function trim_trailing_space_all_source_files() {
for f in $(find_source_files .); do trim_trailing_space $f;done
}

Answer 7

For those who look for efficiency (many files to process, or huge files), using the + repetition operator instead of * makes the command more than twice faster.
With GNU sed:
sed -Ei 's/[ \t]+$//' "$1"
sed -i 's/[ \t]\+$//' "$1" # The same without extended regex
I also quickly benchmarked something else: using [ \t] instead of [[:space:]] also significantly speeds up the process (GNU sed v4.4):
sed -Ei 's/[ \t]+$//' "$1"
real 0m0,335s
user 0m0,133s
sys 0m0,193s
sed -Ei 's/[[:space:]]+$//' "$1"
real 0m0,838s
user 0m0,630s
sys 0m0,207s
sed -Ei 's/[ \t]*$//' "$1"
real 0m0,882s
user 0m0,657s
sys 0m0,227s
sed -Ei 's/[[:space:]]*$//' "$1"
real 0m1,711s
user 0m1,423s
sys 0m0,283s

Answer 8

Just for fun:
#!/bin/bash
FILE=$1
if [[ -z $FILE ]]; then
echo "You must pass a filename -- exiting" >&2
exit 1
fi
if [[ ! -f $FILE ]]; then
echo "There is not file '$FILE' here -- exiting" >&2
exit 1
fi
BEFORE=`wc -c "$FILE" | cut --delimiter=' ' --fields=1`
# >>>>>>>>>>
sed -i.bak -e's/[ \t]*$//' "$FILE"
# <<<<<<<<<<
AFTER=`wc -c "$FILE" | cut --delimiter=' ' --fields=1`
if [[ $? != 0 ]]; then
echo "Some error occurred" >&2
else
echo "Filtered '$FILE' from $BEFORE characters to $AFTER characters"
fi

Answer 9

In the specific case of sed, the -i option that others have already mentioned is far and away the simplest and sanest one.
In the more general case, sponge, from the moreutils collection, does exactly what you want: it lets you replace a file with the result of processing it, in a way specifically designed to keep the processing step from tripping over itself by overwriting the very file it's working on. To quote the sponge man page:
sponge reads standard input and writes it out to the specified file. Unlike a shell redirect, sponge soaks up all its input before writing the output file. This allows constructing pipelines that read from and write to the same file.
https://joeyh.name/code/moreutils/

Answer 10

To remove trailing whitespace for all files in the current directory, I use
ls | xargs sed -i 's/[ \t]*$//'

Answer 11

These answers confused me. Both of these sed commands worked for me on a Java source file:
sed 's/\s\+$/ filename
sed 's/[[:space:]]\+$// filename
for test purposes, I used:
$ echo " abc " | sed 's/\s\+$/-xx/'
abc-xx
$ echo -e " abc \t\t " | sed 's/\s\+$/-xx/'
abc-xx
Replacing all trailing whitespace with "-xx".
#Viktor wishes to avoid a temporay file, personally I would only use the -i => in-place with a back-up suffix. At least until I know the command works.
Sorry, I just found the existing responses a little oblique. sed is straightforward tool. It is easier to approach it in a straightforward way 90% of the time. Or perhaps I missed something, happy to corrected there.

Answer 12

To only strip whitespaces (in my case spaces and tabs) from lines with at least one non-whitespace character (this way empty indented lines are not touched):
sed -i -r 's/([^ \t]+)[ \t]+$/\1/' "$file"