String variables are variables with a name starting with S or gS (for a local or global string variable, respectively), and can store any string with a maximum length defined by the -+max_str_len command line flag (255 characters by default). These variables can be used as input argument to any opcode that exepcts a quoted string constant, and can be manipulated at initialization or performance time with the opcodes listed below.
It is also possible to use string p-fields. The string p-field can be used by many orchestra opcodes directly, or it can be copied to a string variable first:
a1 diskin2 p5, 1
Sname strget p5 a1 diskin2 Sname, 1
Strings within Csound can be expressed using traditional double quotes (" "), an also using {{ }}. The second method is useful to allow ';' and '$' characters within the string without having to used ASCII codes.
Note | |
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String variables and related opcodes are not available in Csound versions older than 5.00. |
Strings can also be linked to a number using strset and strget.
Csound 5 also has improvements in parsing string constants. It is possible to specify a multi-line string by enclosing it within {{ and }} instead of the usual double quote characters (note that the length of string constants is not limited, and is not affected by the -+max_str_len option), and the following escape sequences are automatically converted:
\a alert bell
\b backspace
\n new line
\r carriage return
\t tab
\\ a single '\' character
\nnn the character of which the ASCII code (in octal) is nnn
It can be useful together with the system opcode:
instr 1 ; csound5 lets you make a string with line returns inside double brackets system {{ ps date cd ~/Desktop pwd ls -l whois csounds.com }} endin
And the python opcodes, among others:
pyruni {{
import random
pool = [(1 + i/10.0) ** 1.2 for i in range(100)]
def get_number_from_pool(n, p):
if random.random() < p:
i = int(random.random() * len(pool))
pool[i] = n
return random.choice(pool)
}}
These opcodes perform operations on string variables (note: most of the opcodes run at init time only, and have a version with a "k" suffix that runs at both init and performance time; exceptions to this rule include puts and strget):
strcat and strcatk - Concatenates strings, and stores the result in a variable.
strget - Assigns to a string variable, from strset table at the specified index, or string score p-field.
sprintf - printf-style formatted output conversion, storing the result in a string variable.
sprintfk - printf-style formatted output conversion, storing the result in a string variable at k-rate.
puts - Prints a string constant or variable.
strindex and strindexk - Returns the first occurence of a string in another string.
strrindex and strrindexk - Returns the last occurence of a string in another string.
strsub and strsubk - Returns a substring of the input string.