UNIX

UNIX

Pathname
1. Root
  1. Always starts with forward slash
2. Relatives
  1. Relative parthname are quickly to use than absolute pathnames, because their point of departure is the current working directory rather than the root
3. Absolutes
  1. An absolute pathname identifies a file by starting at the root , irrespective of which directory the user is in at the time
Commands to work with directories
1. Command ls to list the contents of a directory to screen
  1. -a displays all the files in the current directory including hidden files, which are prefixed with a dot
  2. -f identifies the types of files in a listing
  3. -G colorizes screen output so that categories of files can be seen easly
  4. -l displays details about each file in a directory, such as its type, permissions, owner, size stc
  5. -r reverses the order in which the files in a directory would be displayed by default
  6. -t displays files according to their modification times
cat command allows you to view and modify the contents of a file. it also allows you to combine two existing files to create a new one
1. -b numbers all the lines in a file except blank lines
2. -n numbers all the lines in a file
3. -u allows you to prevent the command from buffering screen output. this is useful when the file is large and the system memory is limited
Creating a File
1. touch command to create a new file with the name you specify, default permissions and can modify existing files
2. Redirections before command such as echo, cat or ls is executed, you can redirect its output to a file using the > notation
3. Application Files are often created when you use an application such as vi, or macs text editor. To edit, save an give it a name
rm command to delete files, either simgle or in multiple
1. -r to delete the contents recursively
2. -P Overwrite regular files before deleting them
3. -d like the r option, attempt to remove directories as well as files
4. -v Be verbose when deleting files, displaying each as it is remove
5. -i Request confirmation before removing the specified file
6. -f Attempt to remove files without prompting for confirmation, irrespective of file permission
Permissions
1. read = 4, read files or list the contents of a directory
2. white = 2 to modify a file or create an delete in a directory
3. execute = 1 to run a file, if it's a program or script, or access files in the directory
4. Every file and directory also has three groups "owner" "group" "other user"
wilecards and regular expresion
1. the * wildcard matches zero or more instances of any character
2. the ? wildcard matches a single instance of any character
3. the [ ] wildcard to match sets of chararcters. You can include lists of characters or specify a range
4. the ! wildcard within [ ] matches any chararctes that is not listed in the square brakets
the find command seach a file when you do not know where it is located
1. -atime to find files according to their access time (find /-atime 2)
2. -ctime to find files according to their modification time (fine /-ctime 2)
3. -group to fine files according to their owner (fine /-group <name_group>)
4. -size to fine files according to their size (fine /-size 10)
5. -name fine /home -name <namefile>
grep to search the content within local files using the siyntax grep <options><regular exprexion> <file>
1. -c option suppresses output by printing a count of maching lines for each input file
2. -h to suppress prefixing of filesnames on output when searching multiple files
3. -H prints the filename for each match
4. -i allows you to ignore case distinction in both the pattern and input files
5. -n when you want to prefix each line of output with line number within its input file
6. -v to print nonmatches lines for each input file
7. -w to search for a specific pattern as word

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