current community

your communities

more stack exchange communities

Stack Exchange
tour help
Take the 2-minute tour ×
Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems.. It's 100% free, no registration required.
up vote 12 down vote favorite

This question already has an answer here:

I am writing a script which loops into recent files in a folder and executes a command... 

#!/bin/bash
cd /home/Downloads
recent_files = ($(ls -t | head -20))
for file in "${recent_files[@]}"
do
    ./cmd $file
done

I get the following syntax error:

line 3: syntax error near unexpected token `('
line 3: `recent_files = ($(\ls -t | head -20))'
share|improve this question

migrated from serverfault.com May 4 at 3:29

This question came from our site for system and network administrators.

marked as duplicate by dhag, Anthon, mdpc, Stephen Kitt, Networker May 11 at 11:02

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
3  
I suspect you also want cd $HOME/Downloads –  Michael Durrant May 3 at 13:14
    
I would use recent_files=($(ls -t | head -20)) instead of recent_files = ($(ls -t | head -20)) no space arround equal. –  Archemar May 4 at 8:29
2  
10 upvotes? That is a lot of grateful classmates... –  jasonwryan May 5 at 9:03

5 Answers 5

up vote 24 down vote

Bash variable assignment scheme is var=value i.e. extra spaces are not allowed.

Removing them will correctly assign ls -t | head -20 output as an array.

So your script should be :

#!/bin/bash
cd /home/Downloads
recent_files=($(ls -t | head -20))
for file in "${recent_files[@]}"
do
    ./cmd $file
done
share|improve this answer
up vote 9 down vote

You don't need to store the output in a variable at all:

cd /home/Downloads
command ls -t | head -20 | while read -r file; do
    ./cmd "$file"
done

or even 

command ls -t | head -20 | xargs -L 1 ./cmd

A safer way to work this is with stat. It still doesn't protect you from filenames with newlines, but 

stat -c "%Y %n" * | sort -rn | head -20 | cut -d" " -f2- | xargs -L 1 ./cmd

To be foolproof, find -- probably need GNU tools for the null-byte handling

find . "${find_options[@]}" -printf '%T@ %p\0' | 
sort -zrn |
xargs -0 -L 1 sh -c './cmd "$(echo "$0" | sed "1s/^[0-9.]\\+ //")"'

the find_options array can be used as a placeholder to add filtering directives, such as

find_options=( -type f )
find_options+=( -maxdepth 1 )
find_options+=( -name '*.txt' )

and so on

share|improve this answer
    
Since it is generally recommended that the output of ls should not be used in scripts, I tried to figure out how to do this with find. I got as far as find . -maxdepth 1 -type f -printf '%c\t%f\n' -name '*', but the date is still hard to sort. It's not in epoch format yet. The tab is for use later with cut after sorting. AFAIK, the answer above (and all the others based on using ls) will potentially return directory names as well as file names - which might cause unexpected results with a command which expects to see a regular file. –  Joe May 9 at 2:38
up vote 5 down vote

You have to remove the the spaces around the equal sign.

recent_files=($(ls -t | head -20))

Then it should work.

share|improve this answer
    
Removing the outer parentheses would cause recent_files to be a scalar rather than an array, which the ${recent_files[@]} syntax on the next line indicates is not what the OP wants. –  jwodder May 3 at 3:15
up vote 3 down vote

I think there's a simpler answer...

#!/bin/bash
cd /home/Downloads
for file in $(ls -t | head -20)
do
    ./cmd $file
done
share|improve this answer
up vote 1 down vote

The error message says it all. However, as a help to such problems in the future, you can adopt some practices:

  1. Comment out the line that is throwing up an error like so:
recent_files=($(ls -t | head -20))

and run 

bash -n myScript.sh

This will check errors in the script.

  1. Comment out a block of lines like so:

    : << 'EOF'
lines
of
code
EOF

and run 

bash -n myScript.sh

Using this methodology, you will be able to zoom in on the erroneous line in your script.

Coming back to your specific problem, many have already answered what is causing it - the spaces around the = sign.

share|improve this answer