passphrase via terminal for gnupg

gistfile1.txt

# create file
$ echo hello > fun.txt

# symmetric encryption
$ gpg --verbose --verbose --pinentry-mode loopback --symmetric fun.txt
gpg: enabled compatibility flags:
gpg: using cipher AES256.CFB
gpg: writing to 'fun.txt.gpg'

# decryption
$ gpg --verbose --verbose --pinentry-mode loopback --decrypt fun.txt.gpg
gpg: enabled compatibility flags:
# off=0 ctb=8c tag=3 hlen=2 plen=13
:symkey enc packet: version 4, cipher 9, aead 0, s2k 3, hash 10
	salt 9A79F9F8B4821C30, count 65011712 (255)
gpg: AES256.CFB encrypted data
# off=15 ctb=d2 tag=18 hlen=2 plen=66 new-ctb
:encrypted data packet:
	length: 66
	mdc_method: 2
gpg: encrypted with 1 passphrase
gpg: public key encrypted data: good DEK
# off=36 ctb=a3 tag=8 hlen=1 plen=0 indeterminate
:compressed packet: algo=1
# off=38 ctb=ac tag=11 hlen=2 plen=19
:literal data packet:
	mode b (62), created 1773061811, name="fun.txt",
	raw data: 6 bytes
gpg: original file name='fun.txt'
hello
gpg: decryption okay