Changing from string to array not working as expected in Bash

Question

I want to put the result of the sort method into an array where each cell contains a word. I tried this code but only part of the $file is printed and its not sorted:

#!/bin/bash
for file in `ls ${1}` ; do
    if [[ ! ($file = *.user) ]] ; then
        continue
    fi

    arr=(`sort -nrk4 $file`)
    echo ${arr[*]}

done

Why isnt this working? How can I do this?

Data file:

name1 01/01/1994 a 0
name2 01/01/1994 b 5
name3 01/01/1994 c 2

If I run the sort line only (sort -nrk4 $file), this is whats printed:

name2 01/01/1994 b 5
name3 01/01/1994 c 2
name1 01/01/1994 a 0

When I run the 2 lines above, this is what its printed:

 name1 01/01/1994 a 0

@Mat version 3.00.15(1)-release .. I updated the question with all the script, do u see anything that could be the cause? — Omar
– Omar, Commented May 19, 2012 at 8:55

Dennis Williamson · Accepted Answer · 2012-05-20 16:28:35Z

1

In order for each line of the sort output to be put into its own array element, IFS needs to be set to a newline. To output the array, you need to iterate over it.

#!/bin/bash
for file in $1; do
    if [[ ! $file = *.user ]]; then
        continue
    fi

    saveIFS=$IFS
    IFS=$'\n'
    arr=($(sort -nrk4 "$file"))
    IFS=$saveIFS
    for i in "${arr[@]}"
    do
        echo "$i"
    done

done

Alternatively, don't reset IFS, don't use a loop for output and the following command will output the elements separated by newlines since the first character of IFS is used for the output separator when * is used for the subscript in a quoted context:

echo "${arr[*]}"

Remember, quoting fixes everything.

Don't use ls in a for loop. If $1 may contain globbing, then it should be left unquoted. It not, then it should be quoted in case the directory or filename may contain whitespace characters. Ideally, the contents of $1 should be validated before they're used here.

The comparison operators have higher precedence than the negation operator so the parentheses are unnecessary.

For command substitution, $() is preferred over backticks. They're more readable and easier to use nested.

And finally, when variables are expanded, the should be quoted. Also, @ should almost always be used to subscript arrays.

edited May 20, 2012 at 16:28

answered May 19, 2012 at 11:15

Dennis Williamson

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1 Comment

Dennis Williamson Over a year ago

@Omar: Oh, now I see what's happening. Please see my edited answer.

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