Bash epoch date comparison not working

Question

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

score 2 · Accepted Answer · edited Dec 18 '17 at 12:58

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.

edited Dec 18 '17 at 12:58

Stéphane Chazelas

544,893

answered Dec 18 '17 at 04:39

Ipor Sircer

14,546
1
27
39

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
1

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

Bash epoch date comparison not working

1 Answers1