Bash string to int

bashstring

Here is what I tried doing:

#!/bin/sh
res=`df | awk 'FNR == 2 { print $5 }'`
res2=$((res+0))

Here is my error:

-bash: 53%: syntax error: operand expected (error token is "%")

I Googled 'string to int bash' which showed me $((res+0)) but it doesn't work due to the % in the string (53%). How do I convert it in such a way I can do an if statement such as the one below (but that works)?

if [ "$res2" -ge 50 ]
then
    echo "Your disk >=50% full!"
fi

Best Answer

Let awk do it:

df -P | awk 'NR == 2 { print $5+0; exit }'

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Shell – Write variable containing large text with \n to a file with common shell interpreters. How to do it

You can make a here document and use cat:

$ cat <<EOT >output
$a
EOT
$ wc -l output
40000

I don't know exactly how powerful your Busybox's ash is (it's configurable), but that should work anywhere, even with no builtins at all. It expands the variable value into a quasi-file, which is then given to cat, rather than putting the value itself into the command line.

Since you seem to have literal "\n" in your string that you want to get rid of, you can also use string replacement during parameter subsitution. This can be configured out of Busybox's ash, in which case you'll have to go to sed. If you do have this (non-POSIX) extension, you can use ${var//\\\n/$NEWLINE}:

$ busybox ash
$ foo="x\ny\nz"
$ echo "$foo"
x\ny\nz
$ NEWLINE="
"
$ echo "${foo//\\\n/$NEWLINE}"
x
y
z

This is the same syntax as Bash; ${var/pattern/replacement}, where pattern is global if it starts with /. It seems your ash has a lot configured out of it, so this might not be there at all. In that case you're probably going to have to go with sed, although I guess judicious use of IFS and read would let you work around that and reconstruct a correct string.

linux cron – Email Only Occasionally Sent on Output and Errors

Upon further testing, I suspect the & is messing with your results. As you point out, &>/dev/null is bash syntax, not sh syntax. As a result, sh is creating a subshell and backgrounding it. Sure, the subshell's echo creates stderr, but my theory is that:

cron is not catching the subshell's stderr, and
the backgrounding of the subshell always completes successfully, thus bypassing your || echo ....

... causing the cron job to have no output and thus no mail. Based on my reading of the vixie-cron source, it would seem that the job's stderr and stdout would be captured by cron, but it must be getting lost by the subshell.

Test it yourself in a /bin/sh environment (assuming you do not have a file named 'bar' here):

(grep foo bar) &
echo $?

Best Answer

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Shell – Write variable containing large text with \n to a file with common shell interpreters. How to do it

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