Hello I write simple batch script to backup postgeSQL databases, but I find one strange problem whether the pg_dump command can specify a password?

There is batch script:

 REM script to backup PostgresSQL databases
 @ECHO off

 FOR /f "tokens=1-4 delims=/ " %%i IN ("%date%") DO (

 SET dow=%%i
 SET month=%%j
 SET day=%%k
 SET year=%%l
 )

 SET datestr=%month%_%day%_%year%
 SET db1=opennms
 SET db2=postgres
 SET db3=sr_preproduction
 REM SET db4=sr_production

 ECHO datestr is %datestr%

 SET BACKUP_FILE1=D:\%db1%_%datestr%.sql
 SET FIlLENAME1=%db1%_%datestr%.sql

 SET BACKUP_FILE2=D:\%db2%_%datestr%.sql
 SET FIlLENAME2=%db2%_%datestr%.sql

 SET BACKUP_FILE3=D:\%db3%_%datestr%.sql
 SET FIlLENAME3=%db3%_%datestr%.sql

 SET BACKUP_FILE4=D:\%db14%_%datestr%.sql
 SET FIlLENAME4=%db4%_%datestr%.sql

 ECHO Backup file name is %FIlLENAME1% , %FIlLENAME2% , %FIlLENAME3% , %FIlLENAME4%

 ECHO off
 pg_dump -U postgres -h localhost -p 5432 %db1%  > %BACKUP_FILE1%
 pg_dump -U postgres -h localhost -p 5432 %db2%  > %BACKUP_FILE2%
 pg_dump -U postgres -h localhost -p 5432 %db3%  > %BACKUP_FILE3%
 REM pg_dump -U postgres -h localhost -p 5432 %db4%  > %BACKUP_FILE4%

 ECHO DONE !

Please give me advice

Regards Mick