###BASH Command Chaining/Logical ANDing/ORing###
Command Chaining:
TO run a -> b -> c
ls -lF /etc; pwd;who;ps
Logical ANDing:
Program b will execute only if program a was executed
a&&b&&c
Programs mutually inclusive
Returns a exit status 0 and then run b exit status 0 and then run C
Logical ANDing – runs subsequent based on exit status of 0
ls -l /etc/resolv.conf && grep name /etc/resolv.conf
Logical ORing:
Run subsequent program based on failure of previous
ls -l /etc/resolve.conf || grep name /etc/resolv.conf
Example:
If the file text.txt doesnt exist you can create with ORing
ls -l test.txt || touch test.txt
Combining ANDing ORing
-bash-3.00$ ls -l text.txt || touch test.txt && ls -ltr test.txt
text.txt: No such file or directory
-rw-r--r-- 1 carlosap other 0 Aug 22 00:13 test.txt
BASH for LOOPS
text.txt
1
2
3
LOOPS SYNTAX:
for variable in list; do command variable; done
-bash-3.00$ for i in `cat test.txt`; do echo $i; done
1
2
3
-bash-3.00$ for i in `cat test.txt`; do echo test$i; done
test1
test2
test3