Shell脚本中文件名中的空格

Question

I have a shell script that processes some files. The problem is that there might be white spaces in file names, I did:

#!/bin/sh
FILE=`echo $FILE | sed -e 's/[[:space:]]/\\ /g'`
cat $FILE

So the variable FILE is a file name which is passed in from some other program. It may contain white spaces. I used sed to escape white space with \\ in order to make the command line utilities be able to process it.

The problem is that it doesn't work. echo $FILE | sed -e 's/[[:space:]]/\\\\ /g' echo $FILE | sed -e 's/[[:space:]]/\\\\ /g' itself works as expected, but when assigned to FILE , the escape char \\ disappeared again. As a result, cat will interpret it as more than 1 arguments. I wonder why it behaves like this? Is there anyway to avoid it? And what if there're multiple white spaces, say some terrible file.txt , which should be replaced by some\\ \\ \\ terrible\\ \\ file.txt . Thanks.

Answer 1

Don't try to put escape characters inside your data -- they're only honored as syntax (that is, backslashes have meaning when found in your source code , not your data).

That is to say, the following works perfectly, exactly as given:

file='some   terrible  file.txt'
cat "$file"

...likewise if the name comes from a glob result or similar:

# this operates in a temporary directory to not change the filesystem you're running it in
tempdir=$(mktemp -d "${TMPDIR:-/tmp}/testdir.XXXXXX") && (
  cd "$tempdir" || exit
  echo 'example' >'some  terrible  file.txt'
  for file in *.txt; do
    printf 'Found file %q with the following contents:\n' "$file"
    cat "$file"
  done
  rm -rf "$tempdir"
)

Answer 2

Don't make it more complicated than it is.

cat "$FILE"

That's all you need. Note the quotes around the variable. They prevent the variable from being expanded and split at whitespace. You should always write your shell programs like that. Always put quotes around all your variables, unless you really want the shell to expand them.

for i in $pattern; do

That would be ok.