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Caution: This version of this document is no longer maintained. For the latest documentation, see http://www.qnx.com/developers/docs.

sysctl

Get or set the state of the socket manager

Syntax:

sysctl [-n] name...

sysctl [-n] -w name=value...

sysctl [-n] -a|A

Options:

-a
List all the currently available string or integer values.
-A
List all the known MIB names including tables. Those with string or integer values are be printed with the -a flag; for the table values, the name of the utility to retrieve them is given.
-n
Suppress the printing of the field name and output only its value. This flag is also used for setting shell variables. For example, to save the IP TTL value in the variable ipttl: 
set ipttl=`sysctl -n net.inet.ip.ttl`
-w
If just a MIB style name is given, the corresponding value is retrieved. To set a value specify: this flag, the MIB name followed by an equal sign, and the new value to be used.

Description:

The sysctl utility retrieves the state of the socket manager and allows processes with appropriate privilege to set the state. The state to be retrieved or set is described using a Management Information Base (MIB) stylename, described as a dotted set of components.

The information available from sysctl consists of integers and tables. The tabular information can only be retrieved by special purpose programs such as netstat and arp. The integer information is summarized below. For a detailed description of these variable see sysctl(). The changeable column indicates whether a process with appropriate privilege can change the value.

Name Type Changeable?
net.inet.icmp.errppslimit Integer Yes
net.inet.icmp.maskrepl Integer Yes
net.inet.icmp.returndatabytes Integer Yes
net.inet.ip.allowsrcrt Integer Yes
net.inet.ip.anonportmax Integer Yes
net.inet.ip.anonportmin Integer Yes
net.inet.ip.directed-broadcast Integer Yes
net.inet.ip.forwarding Integer Yes
net.inet.ip.forwsrcrt Integer Yes
net.inet.ip.gifttl Integer Yes
net.inet.ip.hostzerobroadcast Integer Yes
net.inet.ip.lowportmax Integer Yes
net.inet.ip.lowportmin Integer Yes
net.inet.ip.maxflows Integer Yes
net.inet.ip.mtudisc Integer Yes
net.inet.ip.mtudisctimeout Integer Yes
net.inet.ip.redirect Integer Yes
net.inet.ip.subnetsarelocal Integer Yes
net.inet.ip.ttl Integer Yes
net.inet.ipsec.ah_cleartos Integer Yes
net.inet.ipsec.ah_net_deflev Integer Yes
net.inet.ipsec.ah_offsetmask Integer Yes
net.inet.ipsec.ah_trans_deflev Integer Yes
net.inet.ipsec.debug Integer Yes
net.inet.ipsec.def_policy Integer Yes
net.inet.ipsec.dfbit Integer Yes
net.inet.ipsec.ecn Integer Yes
net.inet.ipsec.esp_net_deflev Integer Yes
net.inet.ipsec.esp_trans_deflev Integer Yes
net.inet.ipsec.inbound_call_ike Integer Yes
net.inet.tcp.ack_on_push Integer Yes
net.inet.tcp.compat_42 Integer Yes
net.inet.tcp.cwm Integer Yes
net.inet.tcp.cwm_burstsize Integer Yes
net.inet.tcp.init_win Integer Yes
net.inet.tcp.keepcnt Integer Yes
net.inet.tcp.keepidle Integer Yes
net.inet.tcp.keepintvl Integer Yes
net.inet.tcp.log_refused Integer Yes
net.inet.tcp.mss_ifmtu Integer Yes
net.inet.tcp.mssdflt Integer Yes
net.inet.tcp.reno Integer Yes
net.inet.tcp.recvspace Integer Yes
net.inet.tcp.rfc1323 Integer Yes
net.inet.tcp.rstppslimit Integer Yes
net.inet.tcp.sack Integer Yes
net.inet.tcp.sendspace Integer Yes
net.inet.tcp.slowhz Integer No
net.inet.tcp.syn_bucket_limit Integer Yes
net.inet.tcp.syn_cache_interval Integer Yes
net.inet.tcp.syn_cache_limit Integer Yes
net.inet.tcp.timestamps Integer Yes
net.inet.tcp.win_scale Integer Yes
net.inet.udp.checksum Integer Yes
net.inet.udp.recvspace Integer Yes
net.inet.udp.sendspace Integer Yes
net.inet6.icmp6.errppslimit Integer Yes
net.inet6.icmp6.nd6_delay Integer Yes
net.inet6.icmp6.nd6_maxnudhint Integer Yes
net.inet6.icmp6.nd6_mmaxtries Integer Yes
net.inet6.icmp6.nd6_prune Integer Yes
net.inet6.icmp6.nd6_umaxtries Integer Yes
net.inet6.icmp6.nd6_useloopback Integer Yes
net.inet6.icmp6.nodeinfo Integer Yes
net.inet6.icmp6.rediraccept Integer Yes
net.inet6.icmp6.redirtimeout Integer Yes
net.inet6.ip6.accept_rtadv Integer Yes
net.inet6.ip6.anonportmax Integer Yes
net.inet6.ip6.anonportmin Integer Yes
net.inet6.ip6.auto_flowlabel Integer Yes
net.inet6.ip6.bindv6only Integer Yes
net.inet6.ip6.dad_count Integer Yes
net.inet6.ip6.defmcasthlim Integer Yes
net.inet6.ip6.forwarding Integer Yes
net.inet6.ip6.gifhlim Integer Yes
net.inet6.ip6.hdrnestlimit Integer Yes
net.inet6.ip6.hlim Integer Yes
net.inet6.ip6.kame_version String No
net.inet6.ip6.keepfaith Integer Yes
net.inet6.ip6.log_interval Integer Yes
net.inet6.ip6.lowportmax Integer Yes
net.inet6.ip6.lowportmin Integer Yes
net.inet6.ip6.maxfragpackets Integer Yes
net.inet6.ip6.redirect Integer Yes
net.inet6.ip6.rr_prune Integer Yes
net.inet6.ip6.use_deprecated Integer Yes
net.inet6.ipsec6.ah_net_deflev Integer Yes
net.inet6.ipsec6.ah_trans_deflev Integer Yes
net.inet6.ipsec6.debug Integer Yes
net.inet6.ipsec6.def_policy Integer Yes
net.inet6.ipsec6.ecn Integer Yes
net.inet6.ipsec6.esp_net_deflev Integer Yes
net.inet6.ipsec6.esp_trans_deflev Integer Yes
net.inet6.udp6.recvspace Integer Yes
net.inet6.udp6.sendspace Integer Yes
net.key.blockacq_count Integer Yes
net.key.blockacq_lifetime Integer Yes
net.key.larval_lifetime Integer Yes
net.key.random_int Integer Yes
net.key.spi_max_value Integer Yes
net.key.spi_min_value Integer Yes
net.key.spi_try Integer Yes

Examples:

Check to see if the UDP checksum is enabled: 

sysctl net.inet.udp.checksum

Enable IP forwarding so that the host acts as a router: 

sysctl -w net.inet.ip.forwarding=1

See also:

netstat

sysctl() in the Library Reference

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