Keithley 2601B Reference Manual page 305

Section 6: Instrument programming
String library functions
Function
string.lower(s)
string.rep(s, n)
string.sub(s, i)
string.sub(s, i, j)
string.upper(s)
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Series 2600B System SourceMeter® Instrument Reference Manual
Description
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.
2600BS-901-01 Rev. B / May 2013