| pushBack | R Documentation |
Functions to push back text lines onto a connection, and to enquirehow many lines are currently pushed back.
pushBack(data, connection, newLine = TRUE, encoding = c("", "bytes", "UTF-8"))pushBackLength(connection)clearPushBack(connection)data | a character vector. |
connection | A connection. |
newLine | logical. If true, a newline is appended to each stringpushed back. |
encoding | character string, partially matched. See details. |
Several character strings can be pushed back on one or more occasions.The occasions form a stack, so the first line to be retrieved will bethe first string from the last call topushBack. Lines whichare pushed back are read prior to the normal input from theconnection, by the normal text-reading functions such asreadLines andscan.
Pushback is only allowed for readable connections in text mode.
Not all uses of connections respect pushbacks, in particular the inputconnection is still wired directly, so for example parsingcommands from the console andscan("") ignore pushbacks onstdin.
When character strings with a marked encoding (seeEncoding) are pushed back they are converted to thecurrent encoding ifencoding = "". This may involverepresenting characters as<U+xxxx> if they cannot beconverted. They will be converted to UTF-8 ifencoding = "UTF-8" or left as-is ifencoding = "bytes".
pushBack andclearPushBack() return nothing, invisibly.
pushBackLength returns the number of lines currently pushed back.
connections,readLines.
zz <- textConnection(LETTERS)readLines(zz, 2)pushBack(c("aa", "bb"), zz)pushBackLength(zz)readLines(zz, 1)pushBackLength(zz)readLines(zz, 1)readLines(zz, 1)close(zz)Add the following code to your website.
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