NAME
apply —
apply a command to a list of
arguments
SYNOPSIS
apply |
[-ac]
[-#]
command arguments ... |
DESCRIPTION
apply divides its
arguments into
fixed-size groups and runs
command in turn on each
group.
On each execution of
command, each character sequence of
the form “
%d
” in
command, where
d is a digit from 1
to 9, is replaced with the
d´th argument from the
current argument group. The argument group size is set to the largest such
d found. Any given argument number can be used
arbitrarily many times. (Including zero.)
If no explicit substitution sequences are found in
command, the current argument group is substituted after
command delimited by spaces, and the argument group size
defaults to 1 and can be set with the
-# option.
If the argument group size is set to 0, one argument from
arguments is taken for each execution of
command anyway, but is discarded and not substituted;
thus,
command is run verbatim once for every argument.
The options are as follows:
-
-
- -#
- Set the argument group size. Ignored if explicit
substitutions are used.
-
-
- -ac
- Change the magic substitution character from the default
“
%
” to c.
ENVIRONMENT
The following environment variable affects the execution of
apply:
-
-
SHELL
- Pathname of the shell to use to execute
command. If this variable is not defined, the Bourne
shell is used.
FILES
- /bin/sh
- Default shell.
EXAMPLES
apply echo
*
- Prints the name of every file in the current
directory.
apply -2
diff a1 b1 a2 b2 a3 b3
- Compares the `a' files to the `b' files.
apply -0 who
1 2 3 4 5
- Runs who(1) 5
times.
apply
´ln %1 /home/joe/joe.%1´ *
- Hard-links all files in the current directory into the
directory /home/joe, with their names prefixed with
"joe.".
apply
´cvs diff %1 > %1.diff' *.c
- Diff all C sources in the current directory against the
last checked-in version and store each result in its own output file.
HISTORY
The
apply command appeared in
4.2BSD.
AUTHORS
Rob Pike
RESTRICTIONS
The complete command to be executed on each iteration is assembled as a string
without additional quoting and then passed to a copy of the shell for parsing
and execution. Thus, commands or arguments that contain spaces or shell
metacharacters may behave in unexpected ways.
To protect a shell metacharacter fully it must be quoted twice, once against the
current shell and once against the subshell used for execution. Similarly, for
a shell metacharacter to be interpreted by the subshell it must be quoted to
protect it from the current shell. A simple rule of thumb is to enclose the
entire
command in single quotes ('') so that the current
shell does not interpret any of it.
BUGS
There is no easy way to produce the literal string “%1” in
command.
apply unconditionally inserts "exec" at the
beginning of each copy of
command so compound commands
may not behave as intended.