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% File src/library/base/man/try.Rd
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% File src/library/base/man/try.Rd
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% Part of the R package, https://www.R-project.org
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% Part of the R package, https://www.R-project.org
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% Copyright 1995-2013 R Core Team
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% Copyright 1995-2016 R Core Team
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% Distributed under GPL 2 or later
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% Distributed under GPL 2 or later
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\name{try}
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\name{try}
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\alias{try}
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\alias{try}
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\title{Try an Expression Allowing Error Recovery}
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\title{Try an Expression Allowing Error Recovery}
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\description{
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\description{
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\code{try} is a wrapper to run an expression that might fail and allow
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\code{try} is a wrapper to run an expression that might fail and allow
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the user's code to handle error-recovery.
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the user's code to handle error-recovery.
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}
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}
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\usage{
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\usage{
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try(expr, silent = FALSE)
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try(expr, silent = FALSE,
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outFile = getOption("try.outFile", default = stderr()))
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}
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}
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\arguments{
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\arguments{
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\item{expr}{an \R expression to try.}
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\item{expr}{an \R expression to try.}
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\item{silent}{logical: should the report of error messages be suppressed?}
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\item{silent}{logical: should the report of error messages be
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suppressed?}
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\item{outFile}{a \link{connection}, or a character string naming the
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file to print to (via \code{\link{cat}(*, file = outFile)});
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used only if \code{silent} is false, as by default.}
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}
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}
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\details{
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\details{
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\code{try} evaluates an expression and traps any errors that occur
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\code{try} evaluates an expression and traps any errors that occur
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during the evaluation. If an error occurs then the error
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during the evaluation. If an error occurs then the error
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message is printed to the \code{\link{stderr}} connection unless
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message is printed to the \code{\link{stderr}} connection unless
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\code{try} is implemented using \code{\link{tryCatch}}; for
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\code{try} is implemented using \code{\link{tryCatch}}; for
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programming, instead of \code{try(expr, silent = TRUE)}, something like
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programming, instead of \code{try(expr, silent = TRUE)}, something like
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\code{tryCatch(expr, error = function(e) e)} (or other simple
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\code{tryCatch(expr, error = function(e) e)} (or other simple
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error handler functions) may be more efficient and flexible.
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error handler functions) may be more efficient and flexible.
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It may be useful to set the default for \code{outFile} to
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\code{\link{stdout}()}, i.e., \preformatted{ options(try.outFile = stdout()) }
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instead of the default \code{\link{stderr}()},
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notably when \code{try()} is used inside a \code{\link{Sweave}} code
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chunk and the error message should appear in the resulting document.
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}
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}
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\value{
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\value{
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The value of the expression if \code{expr} is evaluated without error,
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The value of the expression if \code{expr} is evaluated without error,
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but an invisible object of class \code{"try-error"} containing the
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but an invisible object of class \code{"try-error"} containing the
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error message, and the error condition as the \code{"condition"}
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error message, and the error condition as the \code{"condition"}
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