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?
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
why are you doing his homework in full ?
This User Gave Thanks to ghostdog74 For This Post:
1. You have a very large file, named 'ColMe', tab-delimited, you are asked to process. You are told that each line in 'ColMe' has 7 columns, and that the values in the 5th column are integers. Using shell functions (and standard LINUX/UNIX filters), indicate how you would verify that these... (1 Reply)
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1. The problem statement, all variables and given/known data:
Hello,
My name is Jordan and studying at the New Bulgarian University in Sofiya. This is my homework but can... (2 Replies)
1. Write a shell script to print the file names of all files having .txt extension of a given directory after converting to uppercase letters. The input (directory name) should be given as command line argument. The script will also check whether sufficient arguments are passed or not and whether... (1 Reply)
A shell script is a script written for the shell, or command line interpreter, of an operating system. Typical operations performed by shell scripts include file manipulation, program execution, printing text etc.
Shell : In computing, a shell is a piece of software that provides an interface for... (1 Reply)
plz i need code to search about numbers like this :
962785785698
962795565488
962785321565
962777321684
962795979515
i need code to detect just numbers start with "96278"
i need it in awk !!
thanks (1 Reply)
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Write a command to display lines ending with the... (1 Reply)
Discussion started by: elh009
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LEARN ABOUT DEBIAN
rbash
RBASH(1) General Commands Manual RBASH(1)NAME
rbash - restricted bash, see bash(1)RESTRICTED SHELL
If bash is started with the name rbash, or the -r option is supplied at invocation, the shell becomes restricted. A restricted shell is
used to set up an environment more controlled than the standard shell. It behaves identically to bash with the exception that the follow-
ing are disallowed or not performed:
o changing directories with cd
o setting or unsetting the values of SHELL, PATH, ENV, or BASH_ENV
o specifying command names containing /
o specifying a file name containing a / as an argument to the . builtin command
o specifying a filename containing a slash as an argument to the -p option to the hash builtin command
o importing function definitions from the shell environment at startup
o parsing the value of SHELLOPTS from the shell environment at startup
o redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
o using the exec builtin command to replace the shell with another command
o adding or deleting builtin commands with the -f and -d options to the enable builtin command
o using the enable builtin command to enable disabled shell builtins
o specifying the -p option to the command builtin command
o turning off restricted mode with set +r or set +o restricted.
These restrictions are enforced after any startup files are read.
When a command that is found to be a shell script is executed, rbash turns off any restrictions in the shell spawned to execute the script.
SEE ALSO bash(1)GNU Bash-4.0 2004 Apr 20 RBASH(1)