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Diffstat (limited to 'doc/misc/eshell.texi')
| -rw-r--r-- | doc/misc/eshell.texi | 62 |
1 files changed, 45 insertions, 17 deletions
diff --git a/doc/misc/eshell.texi b/doc/misc/eshell.texi index 9f9c88582f3..d643cb50960 100644 --- a/doc/misc/eshell.texi +++ b/doc/misc/eshell.texi @@ -201,7 +201,7 @@ history and invoking commands in a script file. * Aliases:: * History:: * Completion:: -* for loop:: +* Control Flow:: * Scripts:: @end menu @@ -219,12 +219,18 @@ same name; if there is no match, it then tries to execute it as an external command. The semicolon (@code{;}) can be used to separate multiple command -invocations on a single line. A command invocation followed by an -ampersand (@code{&}) will be run in the background. Eshell has no job -control, so you can not suspend or background the current process, or -bring a background process into the foreground. That said, background -processes invoked from Eshell can be controlled the same way as any -other background process in Emacs. +invocations on a single line. You can also separate commands with +@code{&&} or @code{||}. When using @code{&&}, Eshell will execute the +second command only if the first succeeds (i.e.@: has an exit +status of 0); with @code{||}, Eshell will execute the second command +only if the first fails. + +A command invocation followed by an ampersand (@code{&}) will be run +in the background. Eshell has no job control, so you can not suspend +or background the current process, or bring a background process into +the foreground. That said, background processes invoked from Eshell +can be controlled the same way as any other background process in +Emacs. @node Arguments @section Arguments @@ -1008,19 +1014,41 @@ command for which this function provides completions; you can also name the function @code{pcomplete/MAJOR-MODE/COMMAND} to define completions for a specific major mode. -@node for loop -@section @code{for} loop +@node Control Flow +@section Control Flow Because Eshell commands can not (easily) be combined with lisp forms, -Eshell provides a command-oriented @command{for}-loop for convenience. -The syntax is as follows: +Eshell provides command-oriented control flow statements for +convenience. -@example -@code{for VAR in TOKENS @{ command invocation(s) @}} -@end example +@table @code + +@item if @{ @var{conditional} @} @{ @var{true-commands} @} +@itemx if @{ @var{conditional} @} @{ @var{true-commands} @} @{ @var{false-commands} @} +Evaluate @var{true-commands} if @var{conditional} returns success +(i.e.@: its exit code is zero); otherwise, evaluate +@var{false-commands}. + +@item unless @{ @var{conditional} @} @{ @var{false-commands} @} +@itemx unless @{ @var{conditional} @} @{ @var{false-commands} @} @{ @var{true-commands} @} +Evaluate @var{false-commands} if @var{conditional} returns failure +(i.e.@: its exit code is non-zero); otherwise, evaluate +@var{true-commands}. -where @samp{TOKENS} is a space-separated sequence of values of -@var{VAR} for each iteration. This can even be the output of a -command if @samp{TOKENS} is replaced with @samp{@{ command invocation @}}. +@item while @{ @var{conditional} @} @{ @var{commands} @} +Repeatedly evaluate @var{commands} so long as @var{conditional} +returns success. + +@item until @{ @var{conditional} @} @{ @var{commands} @} +Repeatedly evaluate @var{commands} so long as @var{conditional} +returns failure. + +@item for @var{var} in @var{list}@dots{} @{ @var{commands} @} +Iterate over each element of of @var{list}, storing the element in +@var{var} and evaluating @var{commands}. If @var{list} is not a list, +treat it as a list of one element. If you specify multiple +@var{lists}, this will iterate over each of them in turn. + +@end table @node Scripts @section Scripts |