bash continue execution on command failure

Question

#! /bin/bash

while :
do
    filenames=$(ls -rt *.log | tail -n 2)
    echo $filenames
    cat $filenames > jive_log.txt
    sleep 0.1
done

I am trying to read latest 2 files from a directory and join them using bash. However when no files are present in the current directory with an extension .log the command ls -rt *.log fails with error "ls: cannot access *.log: No such file or directory". After the error it looks like the while loop does not execute. AfterWhat do I do so that the infinite loop continues even if one command fails.

Ignore errors using filenames=$(ls -rt *.log 2>/dev/null | tail -n 2) — anubhava
– anubhava, Commented Jun 13, 2014 at 9:44
1.) Use find instead of ls. 2.) Bash exits only if the errexit option set -e is used. 3.) Use set -x to debug your script. — ceving
– ceving, Commented Jun 13, 2014 at 9:46
I am using ls -rt so that I can get the 2 newest files. I suppose find does not support this. Also, tried the set +e, but still did not work. — Vinay
– Vinay, Commented Jun 13, 2014 at 9:54

konsolebox · Accepted Answer · 2014-06-13 09:55:42Z

1

I'm not sure what you mean but perhaps:

for (( ;; )); do
    while IFS= read -r FILE; do
        cat "$FILE"
    done < <(exec ls -rt1 *.log  | tail -n 2) >> jive_log.txt
    sleep 1
done

Note the ls option -1 which prints out files line by line.

Anyhow you can join last two files to jive_log.txt with:

while IFS= read -r FILE; do
    cat "$FILE"
done < <(exec ls -rt1 *.log  | tail -n 2) >> jive_log.txt

Another way is to save it to an array (e.g. with readarray) then pass the last 2 elements to cat.

readarray -t FILES < <(exec ls -rt1 *.log)
cat "${FILES[@]:(-2)}" > jive_log.txt  ## Or perhaps you mean to append it? (>>)

edited Jun 13, 2014 at 9:55

answered Jun 13, 2014 at 9:48

konsolebox

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2 Comments

Vinay Over a year ago

"done <(exec ls -rt1 *.txt | tail -n 2) >> jive_log.txt" throws error. syntax error near unexpected token `<(exec ls -rt *.log | tail -n 2)'

konsolebox Over a year ago

Yeah I forgot to add another <. Please see update.

ceving · Accepted Answer · 2014-06-13 10:05:34Z

1

If you want to sort the output of find, you have to add a sort key at the beginning, which can be removed later on.

find . -name \*.log -printf '%T+\t%p\n' |
sort -r |
head -2 |
cut -f 2-

Using head instead of tail is a bit cheaper.

answered Jun 13, 2014 at 10:05

ceving

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