How do I use a for-each loop to iterate over file

问题:

The following command attempts to enumerate all *.txt files in the current directory and process them one by one:

for line in "find . -iname '*.txt'"; do 
     echo $line
     ls -l $line; 
done

Why do I get the following error?:

ls: invalid option -- 'e'
Try `ls --help' for more information.

回答1:

Here is a better way to loop over files as it handles spaces and newlines in file names:

find . -type f -iname "*.txt" -print0 | while IFS= read -r -d $'\0' line; do
    echo "$line"
    ls -l "$line"    
done

回答2:

The for-loop will iterate over each (space separated) entry on the provided string.

You do not actually execute the find command, but provide it is as string (which gets iterated by the for-loop). Instead of the double quotes use either backticks or $():

for line in $(find . -iname '*.txt'); do 
     echo "$line"
     ls -l "$line"
done

Furthermore, if your file paths/names contains spaces this method fails (since the for-loop iterates over space separated entries). Instead it is better to use the method described in dogbanes answer.

---

To clarify your error:

As said, for line in "find . -iname '*.txt'"; iterates over all space separated entries, which are:

• find
• .
• -iname
• '*.txt' (I think...)

The first two do not result in an error (besides the undesired behavior), but the third is problematic as it executes:

ls -l -iname

A lot of (bash) commands can combine single character options, so -iname is the same as -i -n -a -m -e. And voila: your invalid option -- 'e' error!

回答3:

More compact version working with spaces and newlines in the file name:

find . -iname '*.txt' -exec sh -c 'echo "{}" ; ls -l "{}"' \;

回答4:

Use command substitution instead of quotes to execute find instead of passing the command as a string:

for line in $(find . -iname '*.txt'); do 
     echo $line
     ls -l $line; 
done