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Homework and Emergencies Homework & Coursework Questions Need some help with my homework Post 302494240 by ilikecows on Sunday 6th of February 2011 11:40:23 AM
Old 02-06-2011
1. Because the PATH variable defines the directories your shell looks in for commands you type that aren't built into the shell. For instance if you type ls, and ls isn't an internal shell command, it looks through the directories in PATH for an executable file with the same name as the command you typed and tries to execure it. /bin and /usr/bin are used to store commonly used executable files such as ls, grep, chmod, etc.

2. Because the `` quotes are command substitution quotes. the shell will execute the command between them and then substitute is ouput in place of `command` as if you had typed it. `date` tries to run a command named whatever date outputs on your system.

3. Its easiest to use three seperate commands. If it takes longer to figure out how to do something in one command than it takes to type 3 and computing resources aren't an issue because you are only going to do it once or you have a tiny amount of data, why waste your time trying to figure out how to make a complex command work?
Code:
cat foo1 > newfile
somecommand >> newfile
cat foo2 >> newfile

4. ${d-*} means if d is unset then assign * to d. see the parameter expansion section of the ksh, sh, or bash man page for more info.

5. yes
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mktemp(3C)						   Standard C Library Functions 						mktemp(3C)

NAME
mktemp - make a unique file name from a template SYNOPSIS
#include <stdlib.h> char *mktemp(char *template); DESCRIPTION
The mktemp() function replaces the contents of the string pointed to by template with a unique file name, and returns template. The string in template should look like a file name with six trailing 'X's; mktemp() will replace the 'X's with a character string that can be used to create a unique file name. Only 26 unique file names per thread can be created for each unique template. RETURN VALUES
The mktemp() function returns the pointer template. If a unique name cannot be created, template points to a null string. ERRORS
No errors are defined. EXAMPLES
Example 1 Generate a filename. The following example replaces the contents of the "template" string with a 10-character filename beginning with the characters "file" and returns a pointer to the "template" string that contains the new filename. #include <stdlib.h> ... char *template = "/tmp/fileXXXXXX"; char *ptr; ptr = mktemp(template); USAGE
Between the time a pathname is created and the file opened, it is possible for some other process to create a file with the same name. The mkstemp(3C) function avoids this problem and is preferred over this function. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |Safe | +-----------------------------+-----------------------------+ SEE ALSO
mkstemp(3C), tmpfile(3C), tmpnam(3C), attributes(5), standards(5) SunOS 5.11 15 Sep 2004 mktemp(3C)
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