:is show symbols with no address

[trufae]

[0x56434c8b463d]> :is | grep 0x0
0x0 u 
0x0 f Scrt1.o
0x0 f crtstuff.c
0x0 f radare2.c
0x0 f crtstuff.c
0x0 f 
0x0 f r_sys_getenv
0x0 u __gmon_start__
0x0 f read@GLIBC_2.2.5
0x0 f strncmp@GLIBC_2.2.5
0x0 f malloc@GLIBC_2.2.5
0x0 u _ITM_deregisterTMCloneTable
0x0 f r_str_argv
0x0 f r_log_message
0x0 f free@GLIBC_2.2.5
0x0 f strlen@GLIBC_2.2.5
0x0 u _ITM_registerTMCloneTable
0x0 f __cxa_finalize@GLIBC_2.2.5
0x0 f strstr@GLIBC_2.2.5
0x0 f atoi@GLIBC_2.2.5
0x0 f r_main_radare2
0x0 f __libc_start_main@GLIBC_2.34
0x0 f write@GLIBC_2.2.5
0x0 f r_sys_setenv
0x0 f r_log_match
[0x56434c8b463d]>