Bash – Reading a delimited string into an array in Bash

arraysbashshellstring

I have a variable which contains a space-delimited string:

line="1 1.50 string"

I want to split that string with space as a delimiter and store the result in an array, so that the following:

echo ${arr[0]}
echo ${arr[1]}
echo ${arr[2]}

outputs

1
1.50
string

Somewhere I found a solution which doesn't work:

arr=$(echo ${line})

If I run the echo statements above after this, I get:

1 1.50 string
[empty line]
[empty line]

I also tried

IFS=" "
arr=$(echo ${line})

with the same result. Can someone help, please?

Best Answer

In order to convert a string into an array, please use

arr=($line)

read -a arr <<< $line

It is crucial not to use quotes since this does the trick.

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

Bash – How to check if a directory exists in a Bash shell script

To check if a directory exists in a shell script, you can use the following:

if [ -d "$DIRECTORY" ]; then
  # Control will enter here if $DIRECTORY exists.
fi

Or to check if a directory doesn't exist:

if [ ! -d "$DIRECTORY" ]; then
  # Control will enter here if $DIRECTORY doesn't exist.
fi

However, as Jon Ericson points out, subsequent commands may not work as intended if you do not take into account that a symbolic link to a directory will also pass this check. E.g. running this:

ln -s "$ACTUAL_DIR" "$SYMLINK"
if [ -d "$SYMLINK" ]; then 
  rmdir "$SYMLINK" 
fi

Will produce the error message:

rmdir: failed to remove `symlink': Not a directory

So symbolic links may have to be treated differently, if subsequent commands expect directories:

if [ -d "$LINK_OR_DIR" ]; then 
  if [ -L "$LINK_OR_DIR" ]; then
    # It is a symlink!
    # Symbolic link specific commands go here.
    rm "$LINK_OR_DIR"
  else
    # It's a directory!
    # Directory command goes here.
    rmdir "$LINK_OR_DIR"
  fi
fi

Take particular note of the double-quotes used to wrap the variables. The reason for this is explained by 8jean in another answer.

If the variables contain spaces or other unusual characters it will probably cause the script to fail.

Best Answer

Related Solutions

C# – the difference between String and string in C#

This is the style that Microsoft tends to use in their examples.

Bash – How to check if a directory exists in a Bash shell script

Related Topic