ops102_3_1.pdf

File and Directory Operations OPS102 Week 3 Class 1 Tiayyba Riaz/John Sellens May 21, 2024 Seneca Polytechnic Outline Files in Linux/Unix Learning About Commands File and Directory Operations File Globbing OPS102 W3C1 - File and Directory Operations 1/18 Outline F...

File and Directory Operations OPS102 Week 3 Class 1 Tiayyba Riaz/John Sellens May 21, 2024 Seneca Polytechnic Outline Files in Linux/Unix Learning About Commands File and Directory Operations File Globbing OPS102 W3C1 - File and Directory Operations 1/18 Outline Files in Linux/Unix Learning About Commands File and Directory Operations File Globbing OPS102 W3C1 - File and Directory Operations 2/18 Files in Linux/Unix Files, Files, Files Data is saved in files In Linux/Unix we really like text files For data, presentations, configuration, logs, and more The system and shell provide “easy” ways to deal with files More about file details next week OPS102 W3C1 - File and Directory Operations 3/18 Learning About Commands Manual Labour There is extensive documentation readily available on Linux/Unix systems Less so on Windows, though commands often provide help e.g. "dir /?" The ”man” (manual) command provides access to most documentation Man pages are divided into sections – see "man man" OPS102 W3C1 - File and Directory Operations 4/18 File and Directory Operations Topics Creating and removing directories Moving files and directories Copying files/directories Creating and deleting files Working with file contents OPS102 W3C1 - File and Directory Operations 5/18 Important File Management Skills Create files and directories Read the contents of files Copy files for backup purposes Move or rename incorrectly spelled filenames View text file contents without the danger of editing or corrupting those files. Remove files Check for differences between a couple of files Obtain information regarding the status of a file and information regarding the file’s contents We have learned to do these operations in a GUI, now we will learn how to do them on a command line. OPS102 W3C1 - File and Directory Operations 6/18 File and Directory Operations Linux Windows Usage mkdir mkdir Create directories mv move Move/Rename files/directories - rename Rename files/directories cp copy Create a copy of files/directories rm del Remove files/directories rmdir rmdir Remove empty directories rm -r deltree Recursive directory removal touch - Create empty file/update time - copy nul: file.txt Create empty file OPS102 W3C1 - File and Directory Operations 7/18 Directory Operations Recall the "cd" command - change directory There’s also "pushd" and "popd" These are shell commands (or system library "chdir()") "mkdir" creates one or more directories The "-p" ensures the path/parents exist "rmdir" removes one or more empty directories Recursive remove – "rm -r" – removes non-empty directories OPS102 W3C1 - File and Directory Operations 8/18 File Operations Create files with a text editor Or output from program. output redirection (next week), etc "touch" will create an empty file (limited utility) or change the file’s timestamp Copy and move – "cp" and "mv" – mostly do what you expect One or more sources to a destination Destination can be an existing directory "mv" also renames – moves to a new name Remove – "rm" – removes files or with "-r" it removes directories recursively OPS102 W3C1 - File and Directory Operations 9/18 Working with Text Files Linux/Unix systems have many tools for working with text files, Windows less so. Linux Windows Usage cat copy file con: Display the contents of file type all at once on screen more, less more Display the contents of file one screen at a time head, tail - Display the beginning or end of file file - Determine the type of file In Windows you would typically need add-on programs for most of these. Or WSL: Windows Subsystem for Linux. OPS102 W3C1 - File and Directory Operations 10/18 Working with Text Files (cont’d) Linux Windows Usage sort - Sort the lines of file uniq - Display identical consecutive lines only once cut - Remove undesired columns from your data in file tr - Translate/replace the occurrences of characters grep findstr Find specific lines in a file find - Find files matching specific criteria in the filesystem diff - Show the differences between two files OPS102 W3C1 - File and Directory Operations 11/18 File Globbing File Globbing File globbing is a feature provided by the shell. By using special characters called wildcards, we can write a generic name that the shell will expand into the specific matching names. A wildcard is a symbol with a special meaning that can be used to substitute for one or more characters. When you type a command and press the enter key, bash performs file name expansion on any wildcards on the command line before it executes the command. So you type a short form and it is expanded into the full list of matching files (or directories) before the shell executes the command. e.g. OPS102 W3C1 - File and Directory Operations 12/18 How Does Globbing Work? When the enter key is pressed, the shell automatically expands "*" into the names of all the files and directories in the current working directory before executing the echo command. The echo command never receives "*" as an argument, it only receives the result of the filename expansion. Wildcards can be used with any command such as ls, rm, cp, etc. Example: "rm *.pdf" deletes all pdf files in the current directory. ”glob” is short for ”global” (or so says wikipedia) and was originally a separate command, or so says "man 7 glob" https://en.wikipedia.org/wiki/Glob_(programming) OPS102 W3C1 - File and Directory Operations 13/18 File Globbing: Wildcard Characters The bash shell (like most shells) recognizes 3 types of globbing Windows command has more limited globbing features An asterisk "*" (or star) represents zero or more characters A question mark "?" represents exactly one character (any character) A set of square brackets represents any one character from the list inside the brackets e.g. "[pdq]" represents a p, d, or q. e.g. "[a-m]" represents a lower case letter from the range a through m. e.g. "[a-zA-Z]" represents any single letter. OPS102 W3C1 - File and Directory Operations 14/18 File Globbing: asterisk * The asterisk "*" is interpreted by the shell to generate filenames by matching the asterisk to any combination of characters (even none). When "*" is used with the command ls (or any command) and no path is given, the shell will use filenames in the current directory. Pattern Interpretation *.pdf This expands to all file or directory names that end in.pdf ls *.pdf Lists all files (or directories) with the extension.pdf e.g. myfile.pdf, cities.pdf, 123.pdf rm img*.jpg Delete all files with names starting ”img” and ending ”.jpg” e.g. img001.jpg, imgface.jpg, img500.jpg OPS102 W3C1 - File and Directory Operations 15/18 File Globbing: question mark ? The question mark "?" is interpreted by the shell to generate filenames by matching the question mark to any exactly one character (any character). Pattern Interpretation ls File?.pdf Lists all files (or directories) with names starting with File, followed by any one character, and then ending with.pdf e.g. Filea.pdf, File1.pdf, File2.pdf, FileC.pdf But not File12.pdf – why? rm img?.jpg Delete all files with names starting img, followed by one more character, and ending.jpg e.g. img0.jpg and img2.jpg would be deleted But not img50.jpg OPS102 W3C1 - File and Directory Operations 16/18 File Globbing: square brackets [] A set surrounded by square brackets [] is called a character class. It matches any one of the characters contained in the class. The class may include ranges; order within the class is not important. Pattern Interpretation ls File.pdf List File1.pdf, File2.pdf and File3.pdf (if they exist). It will not list File123.pdf (if it exists) – why? rm img.jpg Delete files that start with img, followed by either 0, 1, or 2, and ending with.jpg. Examples: img0.jpg, img1.jpg and img2.jpg OPS102 W3C1 - File and Directory Operations 17/18 File Globbing: square brackets [] and ! If the first character in a character class is an exclamation mark ! then the class is inverted. i.e. The character class will match any character that is not listed in the class. For example [!a-z] matches any character that is not a lower case letter. [!0-9] matches any character that is not a digit. OPS102 W3C1 - File and Directory Operations 18/18 Test Yourself The command "rm *123??.jpg" will delete which of the files from the following list? Image1230.jpg City12345.jpg Book12391.jpg Pic123me.jpg Img123you.jpg OPS102 W3C1 - File and Directory Operations 19/18