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Need some help in fixing simple bash script below. What it does is to compare dates in epoch format using if else. The script does not work as I intended because it always goes to the first condition DEPLOY all the time.

Even if I set the deploymentDate variable to be greater than currentDate it still goes to the first condition.

Can anyone suggest on how to fix it?

#!/bin/bash 
currentDate=$(date +s% ) 
deploymentDate=1513516201 

if [ "$currentDate" > "$deploymentDate" ] 
then 
    XSL="DEPLOY" 
else 
    XSL="DO NOT DEPLOY" 
fi 
echo $XSL

Output 

DEPLOY
Jeff Schaller
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dimas
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1 Answers1

2

wrong date usage.

  • date +%s with GNU date or compatible, or
  • awk 'BEGIN{srand(); printf "%lu\n", srand()}' with most awk implementations (will be guaranteed by the next version of the POSIX specification)

wrong statement usage:

  • if ((currentDate > deploymentDate)) (ksh/zsh/bash)
  • if [ "$currentDate" -gt "$deploymentDate" ] (POSIX)

Alternatively, you could use UTC dates in the YYYY-mm-dd HH:MM:SS format and use lexical comparison:

currentDate=$(date -u +'%Y-%m-%d %T') 
deploymentDate='2017-12-17 13:10:01' # UTC
if [[ "$currentDate" > "$deploymentDate" ]] # ksh/bash/zsh

if expr "$currentDate" '>' "$deploymentDate" > /dev/null # POSIX

Or numerical comparison with YYYYmmddHHMMSS date formats, but you could run into problems on systems or shells (like mksh) using 32bit integers for arithmetics.

Stéphane Chazelas
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Ipor Sircer
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  • thanks for the answer. I tried using date +%s but it says line 2: +s%: command not found. See my revision – dimas Dec 18 '17 at 04:44
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    @dimas `%s` not `s%` also within command substitution `$(date +%s)` – αғsнιη Dec 18 '17 at 04:50
  • ahhh... thanks guys it's now working. What is the difference with single bracket and double bracket? I saw in some tutorial they are using single bracket for if else? – dimas Dec 18 '17 at 04:57
  • See [`Is [[ ]] preferable over [ ] in Bash?`](https://stackoverflow.com/q/669452/4023950) – αғsнιη Dec 18 '17 at 05:33
  • `[[ x > y ]]` (a ksh/zsh/bash operator) performs a lexical comparison (though typically, you'd have a problem if the deployment date was before September 2001), for a numerical comparison, use `[ "$currentDate" -gt "$deploymentDate" ]` (POSIX) or `((currentDate > deploymentDate))` (ksh, zsh, bash) – Stéphane Chazelas Dec 18 '17 at 12:45