如何根据Solaris中的输入参数计算前“n”个月?

如果有 DateTime 模块已安装,或者您可以从CPAN安装模块(至少安装到您的主目录中):

#!/usr/bin/env perl

use DateTime;

my $in = $ARGV[0] or die "No input";
my ( $year, $month ) = ( $in =~ m/^(\d\d\d\d)(\d\d)$/ ) or die "Wrong format";
my $dt = DateTime->new( year => $year, month => $month );
$dt->subtract( months => 13 );
print $dt->strftime("%Y%m\n");

根据要求,不使用 日期时间 模块:

#!/usr/bin/env perl

my $in = $ARGV[0] or die "No input";
my ( $year, $month ) = ( $in =~ m/^(\d\d\d\d)(\d\d)$/ ) or die "Wrong format";
$month -= 13;
while ( $month < 1 ) {
    $year  -= 1;
    $month += 12;
}
printf "%04i%02i\n", $year, $month;

这也可以通过使用Solaris 10 ksh的基本shell脚本来完成:

previousNMonth()
{
  y=$(echo $1|sed 's/..$//')
  m=$(echo $1|sed 's/^....//')
  m=$((m-$2))
  while [ $m -lt 1 ]; do m=$((m+12)); y=$((y-1)); done
  printf "%04d%02d\n" $y $m
} 

$ previousNMonth 201308 13
201207

如果您使用的是Solaris 11,这里有一个纯shell的ksh93版本,即不依赖外部命令:

previousNMonth()
{
  y=${1:0:4}
  m=$((${1:4:2}-$2))
  while (( m < 1)); do m=$((m+12)); y=$((y-1)); done
  printf "%04d%02d\n" $y $m
}