Here Documents & Here Strings

here_string.sh

#!/bin/bash

LAN_IP="192.168.1.1"
LAN_MASK="255.255.255.0"
LAN_GW="192.168.1.254"


echo "hello world" | wc -w

wc -w <<< "hello world"

grep "dev" <<<`ls -1 /` >/dev/null && echo "Found" || echo "Not found"

grep "windows" <<<`ls -1 /` >/dev/null && echo "Found" || echo "Not found"


cat << EOF > /tmp/a
allow-hotplug eth0
iface eth0 inet static
	   address $LAN_IP
	   netmask $LAN_MASK
	   gateway $LAN_GW	
EOF

# je potreba escapovat, co se nema dosadit/vyhodnotit
cat << EOF > /tmp/b
allow-hotplug eth0
iface eth0 inet static
	   address $LAN_IP
	   netmask $LAN_MASK
	   gateway $LAN_GW	
	   dns-nameservers \$LAN_GW		   
EOF

# 'EOF' - apostrof zajisti nenahrazovani promennych
cat << 'EOF' > /tmp/c
allow-hotplug eth0
iface eth0 inet static
	   address $LAN_IP
	   netmask $LAN_MASK
	   gateway $LAN_GW	
EOF

# <<- pomlcka dovoli cely oblok odsadit od zacatku radku, jinak musi byt EOF na prvnim sloupci
	cat <<- 'EOF' > /tmp/d
	allow-hotplug eth0
	iface eth0 inet static
		   address $LAN_IP
		   netmask $LAN_MASK
		   gateway $LAN_GW	
	EOF

	cat <<- EOF > /tmp/e
	allow-hotplug eth0
	iface eth0 inet static
		   address $LAN_IP
		   netmask $LAN_MASK
		   gateway $LAN_GW	
	EOF

cat <<- KonecTextu > /tmp/f
allow-hotplug eth0
iface eth0 inet static
	   address $LAN_IP
	   netmask $LAN_MASK
	   gateway $LAN_GW	
KonecTextu

vystup.sh

martin@martin:/tmp$ ./here_string.sh 
2
2
Found
Not found
martin@martin:/tmp$ cat a
allow-hotplug eth0
iface eth0 inet static
	   address 192.168.1.1
	   netmask 255.255.255.0
	   gateway 192.168.1.254	
martin@martin:/tmp$ 
martin@martin:/tmp$ cat b
allow-hotplug eth0
iface eth0 inet static
	   address 192.168.1.1
	   netmask 255.255.255.0
	   gateway 192.168.1.254	
	   dns-nameservers $LAN_GW		   
martin@martin:/tmp$ 
martin@martin:/tmp$ cat c
allow-hotplug eth0
iface eth0 inet static
	   address $LAN_IP
	   netmask $LAN_MASK
	   gateway $LAN_GW	
martin@martin:/tmp$ 
martin@martin:/tmp$ cat d
allow-hotplug eth0
iface eth0 inet static
   address $LAN_IP
   netmask $LAN_MASK
   gateway $LAN_GW	
martin@martin:/tmp$ 
martin@martin:/tmp$ cat e
allow-hotplug eth0
iface eth0 inet static
   address 192.168.1.1
   netmask 255.255.255.0
   gateway 192.168.1.254	
martin@martin:/tmp$ 
martin@martin:/tmp$ cat f
allow-hotplug eth0
iface eth0 inet static
   address 192.168.1.1
   netmask 255.255.255.0
   gateway 192.168.1.254	
martin@martin:/tmp$ 

zdroje.md

http://tldp.org/LDP/abs/html/here-docs.html

http://tldp.org/LDP/abs/html/x17837.html