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Diffstat (limited to 'shell-workshop/shell.txt')
| -rw-r--r-- | shell-workshop/shell.txt | 131 |
1 files changed, 0 insertions, 131 deletions
diff --git a/shell-workshop/shell.txt b/shell-workshop/shell.txt deleted file mode 100644 index d98d249..0000000 --- a/shell-workshop/shell.txt +++ /dev/null @@ -1,131 +0,0 @@ -introduce the shell interpreter - POSIX.1-2008 XCU 2.1 - shell reads input from: - a specified file, - '-c' option argument, or - stdin (interactive mode) - shell splits input lines into tokens and parses them - shell expands words - shell performs I/O redirection - shell executes functions, built-in commands, files, etc. -parameters and variables - positional parameters - POSIX.1-2008 XCU 2.5.1 - decimal numbers greater than 0, e.g. $1 and $2 - multiple-digit numbers should be enclosed in braces - assigned with: - shell arguments when shell starts - function arguments when a function is called - can be reassigned using 'set' built-in command - special parameters - POSIX.1-2008 XCU 2.5.2 - @ - all positional parameters - * - all positional parameters - # - number of positional parameters - ? - exit status of most recent command pipeline - - - current option flags - $ - process ID of shell - ! - process ID of most recent background command - 0 - name of shell or shell script - shell variables - POSIX.1-2008 XCU 2.5.3 - HOME - pathname of user's home directory - IFS - delimiters for field splitting - default: <space> <tab> <newline> - LINENO - line number of current script, if any - PATH - list of paths which should be searched for commands - PS1 - prompt value to be expanded and written to standard error - default value: "$ " - PWD - absolute pathname of the current working directory -word expansions - tilde expansion - POSIX.1-2008 XCU 2.6.1 - tilde-prefix: unquoted tilde at the beginning of a word - followed by all unquoted characters until first unquoted slash - login name is all characters in tilde-prefix following tilde - if login name is empty (tilde-prefix == "~") - expanded to value of HOME - else - expanded to home directory associated with login name - parameter expansion - POSIX.1-2008 XCU 2.6.2 - ${expression} or $expression - expression: - parameter - parameter:-word - parameter:=word - parameter:?word or parameter:? - parameter:+word - #parameter - parameter%word - parameter%%word - parameter#word - parameter##word - command substitution - POSIX.1-2008 XCU 2.6.3 - $(command) - or - `command` - expanding: - shell executes command in a subshell - shell replaces substitution with stdout of the command - newlines within command are allowed - nesting - `command1 \`command2 foo\` bar` - $(command1 $(command2 foo) bar) - arithmetic expansion - POSIX.1-2008 XCU 2.6.4 - $((expression)) - expanding: - shell processes expression - shell replaces substitution with value of the expression - arithmetic: - signed long integer precision - decimal, octal, and hexadecimal constants - e.g. 42, 052, 0x2A - operators: - ( ), unary +, unary -, +, -, *, /, % - ~, !, <<, >>, &, ^, | - <, <=, >, >= ==, !=, &&, ||, expr ? expr : expr - =, +=, -=, *=, /=, %=, <<=, >>=, &= ^=, |= - shell variables - if x has an integer value, then the following are equivalent: - $((x + 1)) $(($x + 1)) - field splitting - POSIX.1-2008 XCU 2.6.5 - IFS is a set of delimiters, at which unquoted fields are split - pathname expansion - POSIX.1-2008 XCU 2.6.6 - POSIX.1-2008 XCU 2.13 - performed unless 'set -f' was run - patterns - ? matches any single character - * matches multiple (0 or more) characters - [ opens RE bracket expansion - if pattern does not match any existing files - pattern string is left unchanged -redirection - input redirection - [n]<word - n: optional file descriptor number (default: 0, stdin) - word: name of file - output redirection - [n]>word - [n]>|word - n default: 1, stdout - appending redirected output - [n]>>word |