63 lines
2.1 KiB
Plaintext
63 lines
2.1 KiB
Plaintext
# awk
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an awk-ward (or not really) language.
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some notes in process.
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# some built-in variables
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* FS: input field separator (by default, space)
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* RS: record field separator (by default, newline)
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* NF: number of fields in current record
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* NR: number of current record
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* FNR: number of current record relative to current file
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* OFS: output field separator (by default, space)
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* ORS: output record separator (by default, newline)
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* RLENGTH: length of the string matched by match( )
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$0 represents the entire input record, and $n the nth field in the current record
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=> https://www.tutorialspoint.com/awk/awk_built_in_variables.htm awk tutorial: built-in variables
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# some built-in functions
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=> https://www.tutorialspoint.com/awk/awk_built_in_functions.htm awk tutorial: built-in functions
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=> https://www.tutorialspoint.com/awk/awk_miscellaneous_functions.htm miscellaneous functions
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=> https://www.tutorialspoint.com/awk/awk_string_functions.htm string functions
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## strings
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the index of the first character is 1!
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* index( string, sub) : index of sub as a substring of string
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* length( string )
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* match( string, regex ) : index of the longest match of regex in string
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* split( string, arr, regex ) : split string into array using regex as separato
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* printf( format, expr-list)
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* strtonum(string): useful to convert from hexadecimal (0x prefix) or octal (0 prefix)
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* gsub( regex, sub, string): global substitution of regex with sub in string. if string is ommited, $0 is used
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* sub(regex, sub, string): substitute regex with sub in string, once. if string is omitted, $0 is used
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* substr(string, start, len): returns the substring from start index, with length len. if len is ommitted, it goes until the end of the string
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* tolower( str )
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* toupper( str )
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## misc
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* getline: read the next line
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* next: stops the current processing and start over with next line
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* system: execute the specified command and returns its exit status
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* delete: delete an element from an array, or an array
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# other notes
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## loop through the elements of an array
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```
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arr["a"] = 1
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arr["b"] = 2
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for(key in arr)
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print key ": " arr[key]
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```
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