What does 1 & 2 mean in shell script?
File descriptors are used to identify stdout (1) and stderr (2); command > output is just a shortcut for command 1> output ; You can use &[FILE_DESCRIPTOR] to reference a file descriptor value; Using 2>&1 will redirect stderr to whatever value is set to stdout (and 1>&2 will do the opposite).
What does $# in shell script mean?
$# : This variable contains the number of arguments supplied to the script. $? : The exit status of the last command executed. Most commands return 0 if they were successful and 1 if they were unsuccessful. Comments in shell scripting start with # symbol.
What is ${ 1 in shell script?
$1 is the first command-line argument passed to the shell script. $0 is the name of the script itself (script.sh) $1 is the first argument (filename1) $2 is the second argument (dir1)
What is >& 2 in shell script?
and >&2 means send the output to STDERR, So it will print the message as an error on the console.
What is the meaning of 2 >& 1?
The 1 denotes standard output (stdout). The 2 denotes standard error (stderr). So 2>&1 says to send standard error to where ever standard output is being redirected as well.
What does 2 mean in bash script?
standard error
File descriptor 2 represents standard error. (other special file descriptors include 0 for standard input and 1 for standard output). 2> /dev/null means to redirect standard error to /dev/null . /dev/null is a special device that discards everything that is written to it.
What is Echo $1?
$1 is the argument passed for shell script. then. $1 will be hello. $2 will be 123.
What does grep $1 do?
grep is a program that searches for regular expressions. The first argument for grep is the pattern to look for. In scripts and functions $1 is a reference to the first argument passed to that script or function.
What are the variables $1 $2 $3 etc used for?
Internal variables $1, $2, $3 etc. represent the first, second, third, etc. arguments to the script. $# represents the number of arguments.
What does the 2 >& 1 at the end of the following command mean grep title Fred TXT names 2 >& 1?
4 Answers. The 1 denotes standard output (stdout). The 2 denotes standard error (stderr). So 2>&1 says to send standard error to where ever standard output is being redirected as well.
What does the 2 >& 1 at the end of the following command mean LS names 2 >& 1?
It means redirect the output of stderr (file descriptor 2) to stdout (file descriptor 1).
What does 2>&1 mean in shell scripts?
With Shell Script this is not different, and a quite common idiom, but not so well understood, is the 2>&1, like in ls foo > /dev/null 2>&1. Let me explain what is going on here and why this works the way it does. Simply put, redirection is the mechanism used to send the output of a command to another place.
What does $0 mean in bash script?
$0 is the name of the script itself (script.sh) $ {10} is the tenth argument and must be enclosed in brackets after $9. $ {11} is the eleventh argument. 1 What does $1 mean in Bash?
What is $1 $1 in Linux shell script?
$1 – Linux Shell Scripting Tutorial – A Beginner’s handbook $1 $1 is the first command-line argument passed to the shell script. Also, know as Positional parameters.
What is $0 and $1 and $9 in a script?
$0 is the name of the script itself (script.sh) $1 is the first argument (filename1) $2 is the second argument (dir1) $9 is the ninth argument