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In computing, cp is a command in various Unix and Unix-like operating systems for copying files and directories.The command has three principal modes of operation, expressed by the types of arguments presented to the program for copying a file to another file, one or more files to a directory, or for copying entire directories to another directory.
Cut out selected fields of each line of a file System III cxref: C programming Optional (XSI) Generate a C-language program cross-reference table System V date: Misc Mandatory Display the date and time Version 1 AT&T UNIX dd: Filesystem Mandatory Convert and copy a file Version 5 AT&T UNIX delta: SCCS Optional (XSI) Make a delta (change) to an ...
Copy-on-write (COW), also called implicit sharing [1] or shadowing, [2] is a resource-management technique [3] used in programming to manage shared data efficiently. Instead of copying data right away when multiple programs use it, the same data is shared between programs until one tries to modify it.
/A Append the pipeline content to the output file(s) rather than overwriting them. Note: When tee is used with a pipe, the output of the previous command is written to a temporary file. When that command finishes, tee reads the temporary file, displays the output, and writes it to the file(s) given as command-line argument.
Then, the copy, called the "child process", calls the exec system call to overlay itself with the other program: it ceases execution of its former program in favor of the other. The fork operation creates a separate address space for the child. The child process has an exact copy of all the memory segments of the parent process.
dd is a command-line utility for Unix, Plan 9, Inferno, and Unix-like operating systems and beyond, the primary purpose of which is to convert and copy files. [1] On Unix, device drivers for hardware (such as hard disk drives) and special device files (such as /dev/zero and /dev/random) appear in the file system just like normal files; dd can also read and/or write from/to these files ...
copy letter.txt con would output to stdout, like the type command. Note that copy page1.txt+page2.txt book.txt will concatenate the files and output them as book.txt. Which is just like the cat command). It can also copy files between different disk drives. There are two command-line switches to modify the behaviour when concatenating files:
The test command in Unix evaluates the expression parameter. In most recent shell implementations, it is a shell builtin, even though the external version still exists.In the second form of the command, the [ ] (brackets) must be surrounded by blank spaces (this is because [is a program and POSIX compatible shells require a space between the program name and its arguments).