Tektronix Keithley 2651A Reference Manual page 305

Section 6: Instrument programming
String library functions
This library provides generic functions for string manipulation, such as finding and extracting
substrings. When indexing a string in Lua, the first character is at position 1 (not 0, as in ANSI C).
Indices may be negative and are interpreted as indexing backward from the end of the string. Thus,
the last character is at position –1, and so on.
String library functions
Function
string.byte(s)
string.byte(s, i)
string.byte(s, i, j)
string.char(···)
string.format(
formatstring, ...)
string.len(s)
string.lower(s)
string.rep(s, n)
string.sub(s, i)
string.sub(s, i, j)
string.upper(s)
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Model 2651A High Power System SourceMeter® Instrument Reference Manual
Description
Returns the internal numeric codes of the characters s[i], s[i+1],
···, s[j]. The default value for i is 1; the default value for j is i.
Receives zero or more integers separated by commas. Returns a string
with length equal to the number of arguments, in which each character has
the internal numeric code equal to its corresponding argument.
Returns a formatted version of its variable number of arguments following
the description given in its first argument, which must be a string. The
format string follows the same rules as the printf family of standard C
functions. The only differences are that the modifiers *, l, L, n, p, and h
are not supported and there is an extra option, q. The q option formats a
string in a form suitable to be safely read back by the Lua interpreter; the
string is written between double quotes, and all double quotes, newlines,
embedded zeros, and backslashes in the string are correctly escaped
when written.
For example, the call:
string.format('%q', 'a string with "quotes" and \n new
line')
produces the string:
"a string with \"quotes\" and \
new line"
The options c, d, E, e, f, g, G, i, o, u, X, and x all expect a number as
argument. q and s expect a string. This function does not accept string
values containing embedded zeros, except as arguments to the q option.
Receives a string and returns its length. The empty string "" has length 0.
Embedded zeros are counted, so "a\000bc\000" has length 5.
Receives a string and returns a copy of this string with all uppercase letters
changed to lowercase. All other characters are left unchanged.
Returns a string that is the concatenation of n copies of the string s.
Returns the substring of s that starts at i and continues until j; i and j
can be negative. If j is absent, it is assumed to be equal to -1 (which is
the same as the string length). In particular, the call string.sub(s, 1,
j) returns a prefix of s with length j, and string.sub(s, -i) returns a
suffix of s with length i.
Receives a string and returns a copy of this string with all lowercase letters
changed to uppercase. All other characters are left unchanged.
2651A-901-01 Rev. C October 2021