Thus, you can use $# to check the number of arguments/parameters passed like you did and handle any unexpected situations. (when used within a function) the number of parameters with which a function has been called (set would work there, too). This is explained in the bash man page in the block "Special Parameters".

Mar 15, 2023 · In bash, $0 is a special parameter that holds the name of the script or shell that is currently being executed. It is also known as the “name” or “zeroth argument” of the script. For example, suppose you have a script called “myscript.sh” that you want to run from any directory.

Oct 11, 2023 · Most often, you use the hash or number sign (#) to tell the shell what follows is a comment, and it should not act on it. You can use it in shell scripts and---less usefully---on the command line.

$? is used to find the return value of the last executed command. Try the following in the shell: echo $? If somefile exists (regardless whether it is a file or directory), you will get the return value thrown by the ls command, which should be 0 (default "success" return value). If it doesn't exist, you should get a number other then 0.

Jul 6, 2024 · The dollar sign ($) plays a crucial role in shell scripting. This ranges from argument handling to process management, and even providing information about the script. In this tutorial, we’ll explore the significance of each special dollar sign variable.

Aug 1, 2019 · $? returns the exit value of the last executed command. echo $? prints that value on console. zero implies a successful execution while non-zero values are mapped to various reason for failure. Hence when scripting; I tend to use the following syntax. # do something else. The comparison is to be done on equals to 0 or not equals 0.

Sep 14, 2012 · $# is the number of positional parameters. $- current options set for the shell. $$ pid of the current shell (not subshell). $_ most recent parameter (or the abs path of the command to start the current shell immediately after startup). $IFS is the (input) field separator. $? is the most recent foreground pipeline exit status.

Feb 20, 2011 · $# -The number of arguments supplied to a script. $$ -The process number of the current shell. For shell scripts, this is the process ID under which they are executing. In addition to what cjm said, if the value of $? is 0, then the previous process did terminate normally (or successfully). Otherwise there was some error.

Dec 22, 2020 · That is, "$*" is equivalent to "$1c$2c…", where c is the first character of the value of the IFS variable. If IFS is unset, the parameters are separated by spaces. If IFS is null, the parameters are joined without intervening separators.

When the shell is in POSIX mode (see Bash POSIX Mode), the ‘!’ has no special meaning within double quotes, even when history expansion is enabled. The characters ‘$’ and ‘`’ retain their special meaning within double quotes (see Shell Expansions).