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getopt is a system dependent function, and its behavior depends on the implementation in the C library. Some custom implementations like gnulib are available, however. [6]The conventional (POSIX and BSD) handling is that the options end when the first non-option argument is encountered, and that getopt would return -1 to signal that.
Both the C99 and C++11 standards require at least one argument, but since C++20 this limitation has been lifted through the __VA_OPT__ functional macro. The __VA_OPT__ macro is replaced by its argument when arguments are present, and omitted otherwise. Common compilers also permit passing zero arguments before this addition, however. [4] [6]
The -n option to xargs specifies how many arguments at a time to supply to the given command. The command will be invoked repeatedly until all input is exhausted. Note that on the last invocation one might get fewer than the desired number of arguments if there is insufficient input. Use xargs to break up the input into two arguments per line:
\!:n - argument selector for the n th argument; argument MUST be supplied; n=0 refers to the alias/command name. \!:m-n - argument selector for the arguments from the m th to the n th; arguments MUST be supplied. \!:n-$ - argument selector for the arguments from the n th to the last; at least argument n MUST be supplied.
It also provides many built-in functions which can be used to eliminate the need for shell-scripting in the makefile rules as well as to manipulate the variables set and used in the makefile. [17] For example, the foreach function can be used to iterate over a list of values, such as the names of files in a given directory. [18]
One example of this is Bash, which offers the same grammar and syntax as the Bourne shell, and which also provides a POSIX-compliant mode. [13] As such, most shell scripts written for the Bourne shell can be run in BASH, but the reverse may not be true since BASH has extensions which are not present in the Bourne shell.
The Bourne shell (sh) is a shell command-line interpreter for computer operating systems.It first appeared on Version 7 Unix, as its default shell. Unix-like systems continue to have /bin/sh—which will be the Bourne shell, or a symbolic link or hard link to a compatible shell—even when other shells are used by most users.
A basic statement is one that simply runs a command. The first word is taken as name of the command to be run and may be either an internal command, e.g., echo, or an external command. The rest of the words are passed as arguments to the command. At the basic statement level, here are some of the features of the grammar: