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I am trying to create a timestamp variable in a shell script to make the logging a little easier. I want to create the variable at the beginning of the script and have it print out the current time whenever I issue echo $timestamp. It proving to be more difficult then I thought. Here are some things I've tried:

timestamp="(date +"%T")" echo prints out (date +"%T")

timestamp="$(date +"%T")" echo prints the time when the variable was initialized.

Other things I've tried are just slight variations that didn't work any better. Does anyone know how to accomplish what I'm trying to do?

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2 Answers

up vote 4 down vote accepted

Use a function rather than a fixed variable:

#!/bin/bash

# Define a timestamp function
timestamp() {
  date +"%T"
}

# do something...
timestamp # print timestamp
# dp something else...
timestamp # print another timestamp
# continue...
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Depending on how you intend to use this, you'll still need to use command substitution: echo "$(timestamp): something happened". –  chepner Jun 12 at 13:16
 
Works perfect, Thanks. –  dan08 Jun 12 at 13:40
up vote 0 down vote

Use command substitution:

timestamp=$( date +%T )
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This is what I already tried and it only prints out the time when the variable was initialized. –  dan08 Jun 12 at 13:09
1  
@dan08: That's how variables work. Use a function if you want dynamic output. –  choroba Jun 12 at 13:09

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