file as input for script

Question

I have a simple script (timeconvert.sh) that converts seconds into hh:mm:ss format and writes it to a file timeremain.out:

#!/bin/bash
#convert sec to h:m:s
secs=${1:?}

h=$(( secs / 3600 ))
m=$(( ( secs / 60 ) % 60 ))
s=$(( secs % 60 ))

printf "%02d:%02d:%02d\n" $h $m $s > timeremain.out

I am trying to get it to read a file secremain.out as the input for the script but none of the following work:

cat secremain.out | ./timeconvert.sh
./timeconvert.sh < secremain.out

Can anyone suggest the proper syntax to use or an edit to the script to read the file directly?

John Kugelman · Accepted Answer · 2013-04-03 21:27:01Z

2

Your script reads the seconds from $1 so you can either pass them in on the command line:

secs=$(cat secremain.out)
./timeconvert.sh $secs

# or

./timeconvert.sh $(cat secremain.out)

Or you can change your script to read from stdin:

#!/bin/bash
#convert sec to h:m:s
read secs

If you do the latter then it can read from the file the way you wrote:

cat secremain.out | ./timeconvert.sh
./timeconvert.sh < secremain.out

answered Apr 3, 2013 at 21:27

John Kugelman

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1 Comment

glenn jackman Over a year ago

Note: $(<file) is a bash shortcut for $(cat file)

Gilles Quénot · Accepted Answer · 2013-04-03 21:52:43Z

0

With this script

: you can both use STDIN or an argument, the script detect itself the context :

#!/bin/bash
#convert sec to h:m:s

if [[ -t 0 ]]; then
    secs=${1:?}
else
    read secs
fi

h=$(( secs / 3600 ))
m=$(( ( secs / 60 ) % 60 ))
s=$(( secs % 60 ))

printf "%02d:%02d:%02d\n" $h $m $s

Usage Examples

./script.sh 120

or

echo 120 | ./script.sh

edited Apr 3, 2013 at 21:52

answered Apr 3, 2013 at 21:46

Gilles Quénot

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