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Q. How can I display or show today’s UNIX computer date from a shell script using echo command? How do I store date command output to a variable?
A. Date command is use to print or set the system date and time under Linux/Unix like operating systems. However some time you need to include today’s date in shell script. You need to use command substitution in your shell script to display today’s date. Bash/sh shell performs the expansion by executing command and replacing the command substitution with the standard output
of the command, with any trailing newlines deleted. Command substitution allows the output of a command to replace the command name. You can use following syntax:
For example, type the following at shell prompt to display today’s date:
$ echo "Today is $(date)"
Today is Sat Jan 28 15:48:11 IST 2006
Here is sample script, that stores today’s date in TODAY and hostname in HOST variable:
#!/bin/bash TODAY=$(date) HOST=$(hostname) echo "-----------------------------------------------------" echo "Date: $TODAY Host:$HOST" echo "-----------------------------------------------------" # add rest code...
Save above script and execute it. See working shell script that notify admin user if Linux/FreeBSD system load crossed certain limit
Q. How do I find out if my Lan (NIC) card working at full or halt duplex mode / speed under Linux?
A. LAN card or NIC is use to send and receive data. Technically, we use word Duplex for this functionality. Full duplex means you are able to send and receive data (files) simultaneously. In half duplex, you can either send or receive data at a time (i.e. you cannot send receive data (files) simultaneously). Obviously, full duplex gives you best user experience. However, how can I find out whether I am using full duplex/half duplex speed/mode?
Task: Find full or half duplex speed
You can use dmesg command to find out your duplex mode:
# dmesg | grep -i duplex
eth0: link up, 100Mbps, full-duplex, lpa 0x45E1
Uss ethtool to display or change ethernet card settings. To display duplex speed, enter:
# ethtool eth1
Settings for eth1: Supported ports: [ TP ] Supported link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Full Supports auto-negotiation: Yes Advertised link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Full Advertised auto-negotiation: Yes Speed: 10Mb/s Duplex: Full Port: Twisted Pair PHYAD: 0 Transceiver: internal Auto-negotiation: on Supports Wake-on: umbg Wake-on: g Current message level: 0x00000007 (7) Link detected: yes
You can also use mii-tool to find out your duplex mode. Type following command at shell prompt:
eth0: negotiated 100baseTx-FD flow-control, link ok
- 100baseTx-FD: 100Mbps full duplex (FD)
- 100baseTx-HD: 100Mbps half duplex (HD)
- 10baseT-FD: 10Mbps full duplex (FD)
- 10baseT-HD: 10Mbps half duplex (HD)
mii-tool utility checks or sets the status of a network interfaceÃ¢â‚¬â„¢s Media Independent Interface (MII) unit. Most fast ethernet adapters use an MII to autonegotiate link speed and duplex setting. If you are using old card then this utility may not work (use dmesg command).
This utility is useful for forcing specific Ethernet speed and duplex settings too, setup 100Mbps full duplex speed under Linux:
# mii-tool -F 100baseTx-FD
Setup 10Mbps half duplex:
# mii-tool -F 10baseT-HD
You can find more information about setting duplex speed here using ethtool command.
Updated for accuracy!