Bash: start date less than equal to end date - bash

Question

#!/bin/bash
# slightly malformed input data
input_start=2014-11-1
input_end=2016-01-1
# After this, startdate and enddate will be valid ISO 8601 dates,
# or the script will have aborted when it encountered unparseable data
# such as input_end=abcd
startdate=$(date -I -d "$input_start") || exit -1
enddate=$(date -I -d "$input_end") || exit -1
m="$startdate"
while [ "$m" != "$enddate" ]; do
echo $m
m=$(date -I -d "$m + 1 month")
done
"Script is running fine but when I want to change the While loop condition i.e '<=' 'less then or equal to' its giving error even I tried using "-le".What I want to do here is startdate <= enddate in while loop. Can anyone suggest what needs to done to overcome this issue.
Same Code

Answer 1

-le is for numeric data. 2014-11-01 is not a number. Use < or >. (You need to escape them as \< or \>. Or use [[ instead of [.)
effectively, change
while [ "$m" != "$enddate" ]; do
to
until [ "$m" \> "$enddate" ]; do
or
until [ "$m" '>' "$enddate" ]; do
or
until [[ "$m" > "$enddate" ]]; do
Alternately, use seconds since epoch instead of ISO8601 format.
while [ "$(date -d "$m" +%s)" -le "$(date -d "$enddate" +%s)" ]; do

Answer 2

With dateutils' datetest this is simple:
$ datetest 2014-11-1 --le 2016-01-1 ; echo $?
0
$ datetest 2014-11-1 --gt 2016-01-1 ; echo $?
1
Then again, what you want is simply done by dateseq, which also happens to be a tool of the dateutils suite.
$ dateseq 2014-11-1 +1mo 2016-01-1
2014-11-01
2014-12-01
2015-01-01
2015-02-01
2015-03-01
2015-04-01
2015-05-01
2015-06-01
2015-07-01
2015-08-01
2015-09-01
2015-10-01
2015-11-01
2015-12-01
2016-01-01
Disclaimer: I am the author of the package.