arp -aFor a list of the currently available/reachable Ip's. See if the IP you are trying to ping is listed there.For additional information, follow the stack overflow link here.http://superuser.com/questions/453933/pinging-a-machine-on-my-local-network-gets-an-unreachable-response-from-my-own 
where
|
|
|
Detach dbx from the target and leave the process in a stopped state. This option allows temporary application of other /proc-based debugging tools that might be blocked due to exclusive access. For an example, see Detaching dbx From a Process.
|
The tests below are test conditions provided by the shell: -b file = True if the file exists and is block special file. -c file = True if the file exists and is character special file. -d file = True if the file exists and is a directory. -e file = True if the file exists. -f file = True if the file exists and is a regular file -g file = True if the file exists and the set-group-id bit is set. -k file = True if the files' "sticky" bit is set. -L file = True if the file exists and is a symbolic link. -p file = True if the file exists and is a named pipe. -r file = True if the file exists and is readable. -s file = True if the file exists and its size is greater than zero. -s file = True if the file exists and is a socket. -t fd = True if the file descriptor is opened on a terminal. -u file = True if the file exists and its set-user-id bit is set. -w file = True if the file exists and is writable. -x file = True if the file exists and is executable. -O file = True if the file exists and is owned by the effective user id. -G file = True if the file exists and is owned by the effective group id. file1 –nt file2 = True if file1 is newer, by modification date, than file2. file1 ot file2 = True if file1 is older than file2. file1 ef file2 = True if file1 and file2 have the same device and inode numbers. -z string = True if the length of the string is 0. -n string = True if the length of the string is non-zero. string1 = string2 = True if the strings are equal. string1 != string2 = True if the strings are not equal. !expr = True if the expr evaluates to false. expr1 –a expr2 = True if both expr1 and expr2 are true. expr1 –o expr2 = True is either expr1 or expr2 is true.http://www.unix.com/shell-programming-and-scripting/81862-how-check-if-file-exists-using-if-statement.html
-bash-4.1$ uname -r
1.7.17(0.262/5/3)
-bash-4.1$ uname -r | awk ' BEGIN { FS="[ , .]"} {print $1 }'3. NF - Number of Fields
1
-bash-4.1$ uname -r | awk ' BEGIN { FS="[ , .]"} {print $2 }'
7
-bash-4.1$ uname -r | awk ' BEGIN { FS="[ , .]"} {print $3 }'
17(0
-bash-4.1$ uname -r | awk ' BEGIN { FS="[ , .]"} {print $4 }'
262/5/3)
Example : alias l='ls -l'
.bash_profile file is a shell script that is executed each time you log in
2. type - Used to determine whether the command is an executable, an alias or a function.
today is a function
today ()
{
echo "print data"
}
7. Export - In a way, used to make variables global-bash-4.1$ uname -s | tr -d /
CYGWIN_NT-6.1-WOW64
-bash-4.1$ uname -s | tr -d C
YGWIN_NT-6.1-WOW64
-bash-4.1$
/usr/bin/cat9. whereis - Locates the binary, source and manual page files for a command.
-bash-4.1$ which -p cat
-bash-4.1$ whereis cat10.env - used to print the env variables or to set certain values temporarily.
cat: /bin/cat.exe /usr/bin/cat.exe /usr/share/man/man1/cat.1.gz
-bash-4.1$ id12. sed
uid=500(Administrator) gid=513(None) groups=513(None),545(Users)
-bash-4.1$ id -n
-bash-4.1$ echo $$18. mktemp - The secure way of creating temporary files
3768
tempfoo=`basename $0`
TMPFILE=`mktemp -t ${tempfoo}` || exit 1
echo "program output" >> $TMPFILE -t is now deprecated. UseUsemktemp ${tempfoo}.XXXXXX
Read below for a discussion on mktemp against $$ for creating temporarily files. http://stackoverflow.com/questions/78493/what-does-mean-in-the-shell (Taken from man) OPTIONS
-a, --all
show processes of all users
-e, --everyone
show processes of all users
-f, --full
show process uids, ppids
-h, --help
output usage information and exit
-l, --long
show process uids, ppids, pgids, winpids ps -W : Shows windows as well as cygwin processes
ps -p p_id : Details of a specific processExample of ps -f:Without quotes :
-bash-4.1$ v=ps -a
-bash: -a: command not found
With quotes
-bash-4.1$ v='ps -a'
-bash-4.1$ $v
PID PPID PGID WINPID TTY UID STIME COMMAND
7368 3768 7368 3672 pty0 500 07:16:49 /usr/bin/ps
3768 3916 3768 1492 pty0 500 08:14:12 /usr/bin/bash
3916 1 3916 3916 ? 500 08:14:12 /usr/bin/mintty
-a, --all
print all current settings in human-readable form
-g, --save
print all current settings in a stty-readable form
-F, --file=DEVICE
open and use the specified DEVICE instead of stdin