Specifications for each class

Insert in the relevant section:

1. Shell

@usage [CURRENT DIR] $: command options input. There's no strict sequence requirements for options and input. @note The input arguments or path can be relative or absolute, in quotes or without quotes, with backslash or front slash. Take special consideration for using characters like /, ', ", |, they need to be escaped properly using quotes or back slash. The termination function is by entering ctrl-z to terminate a running tool, the char has to be input with enter key hit. The shell will try it’s best to stop the running thread, if it’s really not able to stop the thread, the program will stop for safety. User are not allowed to use ‘~’ to denote home directory. Shell does not support any type of logic operation like >. @success It will print the returning string, or nothing if returned null, or a blank line if returned empty string. @exceptions If any error occurs where status code not equal to zero, the error will print through stderr stream.

2. Cat

@usage cat [ - ] [string | path] @options cat [filename] : contents of file cat [filename1] [filename2] : contents of both files cat - filename : prints stdin followed by file's content when used with pipe cat - : prints stdin when used with pipe @note If files extensions are such that they not readable properly (eg: pdf), it might display garbage values. ls | cat and ls | cat - will print as expected (contents of that directory or in other words standard input it receives from the ‘from’ tool). Prioritizes args over stdin i.e. if there are args in front, it will execute them and ignore stdin eg: ls | cat file1.txt will print the contents of file1 and not the contents of current directory@note @success @exceptions

3. Echo

Prints the user input as it is. @usage echo [ | string] @options echo word: Prints word echo “word”: Prints word echo “”“word”””: Prints word echo ‘’’word’’’: Prints word echo ‘“word”’: Prints “word” (To look for word in double quotes, it needs to escaped by single quotes before and after the double quotes) echo word\n : Prints echo word\n echo word word2 :Prints word word2 @note Removes the first enclosing (single and double) quotes pair- it finds the first matching pair and removes them. If there is an unmatched quote, it just prints it. Does not escapes any escape sequences like \n \t. If the command is followed by no input, the output with a new line. @success @exceptions

4. Grep

Searches for pattern in a file @usage grep [-A | -B | -C | -c | -o | -v | -help] pattern [path] @options grep -A NUM filename: Print NUM lines of trailing context after matching lines grep -B NUM filename: Print NUM lines of leading context before matching lines grep -C NUM filename: Print NUM lines of output context grep -c “pattern” filename : Print a count of matching lines with pattern grep -c ‘“pattern”’ filename : Print a count of matching lines with “pattern”(pattern surrounded by double quotes) grep -c “pattern” file1 file2 : Print a count of matching lines containing pattern for both files grep -o “pattern” filename: Show only the part of a matching line that matches PATTERN grep -v “pattern” filename: Select non-matching (instead of matching) lines grep -help : Brief information about supported options grep -o -v “pattern filename: Provides the conjunction of results from both options grep - ‘pattern’ filename: Provides the same output as compared to pattern surrounded by double quotes grep - filename: Provides the same output even without surrounding quotes if the pattern consists of one word grep - “pattern” file1 file2: Provides the output after executing the command on both files grep filename: Prints the command since no option was provided @note @success @exceptions

4. Move

Move a file/folder to a given location @usage move [path] [path] … [path to folder] @options move file1 file2 - Moves file1 contents into file2 move /../file1 file2 - Moves file1 contents into file2 move "file1" "file2" - Moves file1 contents into file2 move file1 newfile - Creates newfile and moves file1 contents into newfile move file1 folder - Moves file1 into folder move file1 newfolder - Moves file1 into newfolder move folder1 folder2 - Moves contents of folder1 into folder2 move folder1 newfolder - Moves folder1 into newfolder move file1 file2 file3 folder1 - Moves file1, file2, file3 in folder1 move folder1 folder2 file3 newfolder - Moves folder1, folder2, file3 into newfolder @note @success @exceptions

5. Delete

Delete a file or folder @usage delete [path] @options delete file1 - Deletes file1 delete relativepath1 - Converts relativepath to absolutepath and deletes file1 delete /../file1 - Deletes file1 delete "file1" - Deletes file1 delete newfile - Does nothing delete folder1 - Deletes folder and all its contents @note @success @exceptions

6. Copy

copy a file/folder to a given location @usage copy [path1] [path2] … [path to folder] @options copy file1 file2 Copies file1 contents into file2 copy /../file1 file2 Copies file1 contents into file2 copy "file1" "file2" Copies file1 contents into file2 copy file1 newfile Creates newfile and copies file1 contents into newfile copy file1 folder Copies file1 contents into folder copy file1 newfolder Creates newfolder and copies file1 contents into newfolder copy folder1 folder2 Copies contents of folder1 into folder2 copy folder1 newfolder Creates newfolder and copies folder1 contents into newfolder copy file1 file2 file3 folder1 Copies/Replaces file1, file2, file3 in folder1 copy folder1 folder2 file3 newfolder - Creates and copies folder1, folder2, file3 into newfolder @note @success @exceptions

7. PWD

Show the current directory @usage pwd @note pwd tool does not take in any arguments or stdin, thus it could not be piped to. It will set the initial path to the directory where the program start. @success return a string showing the absolute path of current working directory. @exceptions Cannot find working directory

8. Ls

Lists all the files and subdirectories in the current directory or provided class

@usage ls [-a | -R] [path] @options ls : Lists all files in current directory. ls [path] : Lists all files in the given path. ls -a : Lists all files including hidden files in current directory. ls -a [path] : Lists all files including hidden files in the given path ls -R : Lists all the files (absolute path) in the current directory and subdirectories ls -R [path] : Lists all the files (absolute path) in the given path. ls -a -R : Combination of functions above ls file : Prints file path if it exists in the file system. @note [path] could be either an absolute file or a relative path. If multiple path is given as arguments, only the first argument will be entertained. Ls tool does not allow std, thus can not be pipe to. The recursive variable is printed in absolute path to show the hierarchical structure. @success return the list of file names or path in the @exceptions invalid input path not exist retrieve file list error

10. Cd

Changes directory to a given location

@usage cd [path] @options cd Changes to the home directory. cd [path] : Changes current path to the new path. cd [.. | .] : Changes to parent directory or stay at current directory. @note [path] could be either an absolute file or a relative path. If multiple path is given as arguments, only the first argument will be entertained. Cd does not allow std, thus can not be pipe to. Cd tool will always try to return the Canonical Path of the new directory which is the most simplified and recognizable. It does not allow user to use ‘~’ to denote home directory. @success returns an empty string, but will not create a new line in the output. @exceptions invalid input path not exist path is not directory

11. Sort

Check or sort one or more files @usage sort [options] [path] @options sort [path] : sort the file and paste out the result. sort -c [path] : check if the file is sorted or not, if not show the un-sorted line. sort -help : Brief information about supported options @note [path] could be either an absolute file or a relative path. If multiple path is given as arguments, they will be append together and sort as one file. Stdin must be denoted as “-” when using with other file names, otherwise stdin is not entertained. You cannot use two "-" in the command. @success returns the corresponding result as differed by functions. @exceptions invalid input path not exist path is not file

12. Uniq

Return unique lines of one or more files @usage uniq [options] [path] @options uniq [path] : sort the file and paste out the result. uniq -i [path] : Ignore differences in case when comparing lines. uniq -f [NUM] [path] : Skips NUM fields on each line before checking for uniqueness. Use a null string for comparison if a line has fewer than n fields. Fields are sequences of non-space non-tab characters that are separated from each other by at least one space or tab. uniq -help : Brief information about supported options @note [path] could be either an absolute file or a relative path. If multiple path is given as arguments, they will be append together and sort as one file. Stdin must be denoted as “-” when using with other file names, otherwise stdin is not entertained. You can only use either a file or stdin. It does not work for multiple files. @success returns the corresponding result as differed by functions. @exceptions invalid input path not exist path is not file

13. Cut

Returns characters at specified positions from every line in a file @usage cut [options] [character_positions] [path] cut [path]: prints all the file contents on the console @options cut -c 1,2-4,5 [path] : prints all the characters at positions from each line. cut -d delim -f 1,2-4,5 [path]: separates characters by delimiter and prints
cut : stdin, if it exists, is treated as file contents to be used by cut cut [options] : stdin used as file contents cut - : "-" is replaced by stdin cut -c [character_positions] - : "-" is replaced by stdin cut -d "," -f [character_positions] : "-" is replaced by stdin @note [path] could be either an absolute file or a relative path. Stdin must be denoted as “-” when using with other file names, otherwise stdin is not entertained. @success returns the corresponding result as differed by functions. @exceptions Invalid command path does not exist invalid options No arguments and no standard input. missing arguments and stdin

14. Paste

returns contents of files in parallel on the console @usage paste [options] [file ..] @options paste -d delim [file1 ..]: file content printed in parallel separated by delimiter. paste -s [file1 ..] : paste appends the data in serial rather than in parallel. paste : Stdin treated as file contents to be used by paste paste [options] : stdin, if it exists, is used as file contents paste - [file2 ..] : "-" is replaced by stdin which contains file contents paste [file1 ..] - : "-" is replaced by stdin paste -s - [file2 ..] : "-" is replaced by stdin paste -d "," [file1 ..] - : "-" is replaced by stdin @note [path] could be either an absolute file or a relative path. Stdin must be denoted as “-” when using with other file names, otherwise stdin is not entertained. @success returns the corresponding result as differed by functions. @exceptions Wrong command invalid options Error: No such file or directory path does not exist

15. Comm

compares two sorted files line by line @usage comm [path1] [path2] @options comm -c file1 file2 : check that the file1 and file2 contents are correctly sorted, even if all input lines are pairable. Terminates if any of the file contents are unsorted. comm -d file1 file2 : does not check that the input is correctly sorted comm - file2 : compares file2 with contents received from stdin comm file1 - : compares file1 with contents received from stdin comm -c - file2
comm -d file1 - comm -help : Brief information about supported options comm - -c -help : help gets priority over other options @note [path] could be either an absolute file or a relative path. When no file is present (denoted by "-"), standard input is used. @success returns the corresponding result as differed by functions. @exceptions comm - - Wrong command invalid options

16. Wc

prints the number of bytes, words, and lines in given files @usage wc [options] [path] @options wc -m [path] : Prints only the character counts wc -w [path]: Print only the word counts wc -l [path]: Print only the newline counts wc -help [path]: Brief information about supported options wc -m - : stdin used as file contents wc -w - : stdin used as file contents wc -l - : stdin used as file contents @assumption:wc -l gives the number of new line characters. @note [path] could be either an absolute file or a relative path. When no file is present (denoted by "-"), standard input is used. Since pipe adds an extra new line, cat file1 | wc -l - results in 1 + actual lines in stdin @success returns the corresponding result as differed by functions. @exceptions No such file or directory invalid options