A sequence expression takes the form {x..y}, where x and y are either integers or single characters. When integers are supplied, the expression expands to each number between x and y, inclusive. When characters are supplied, the expression expands to each character lexicographically between x and y, inclusive. Note that both x and y must be of the same type.
Brace expansion is performed before any other expansions, and any characters special to other expansions are preserved in the result. It is strictly textual.
There is no 26 there when the brace expansion is attempted. The 1 and the literal string "$CAP" are an invalid sequence expression at that stage.
---------- Post updated at 07:20 PM ---------- Previous update was at 07:15 PM ----------
Brace expansion is an extension to the POSIX sh standard. Different posix-like shells perform it at different times. bash performs it before all other expansions while ksh leaves it for much later (after parameter expansion and command substitution and field splitting).
---------- Post updated at 07:46 PM ---------- Previous update was at 07:20 PM ----------
I forgot to mention, if you want to loop over the elements of an array, there's a much simpler way to do it:
The * and @ subscripts are analogous to the $* and $@ special parameters used by the shell to handle script arguments.
We have a script that runs in ksh on HP-UX 11.11. It takes three arguments. The last argument can be a filename or wildcard character. For example:
script -s hello -t goodbye '*.d*'
In a case such as this, I would wrap single quotes around the final argument because I dont want the shell to... (4 Replies)
#!/usr/bin/bash
if
then
echo "Not valid arguments entered. Just username should be entered."
else
USER_NAME=$1
FILE_NAME=$USER_NAME.info
UNN=STUDIN\\\\$1
echo $UNN
last STUDIN\\\\$1
last UNN
If I type `last STUDIN\\eip060` it works but if I try to expand it with variable it is... (5 Replies)
I have a script that takes an option for server pools to run the script against. The option is given as a comma separated list (ie, -p 201,204,301).
I'm using eval and brace expansion to get those pool numbers into an array. It works fine unless only 1 pool number is given. Here's the code:
... (5 Replies)
I'm in the habit of using the following type of loop structure:
for num in `seq $1 $2`
do
command
doneWhile `seq $1 $2` is not exactly a huge resource hog, I would like to learn a better way. It seems that brace expansion is a good way to go:
for num in {3..10}The problem, though, is... (2 Replies)
There is a file as:
....... some text
timing () {
capacitance : 9.0;
incap : 0.8;
cell_fall () {
values ("8.9","7.8");
}
}
........ some more text
#######
Is there a way to directly find closing brace "{" of timing () block "{" ? (2 Replies)
i write a batch file , here is the content.
dirname='date +%Y-%m-%d'
mkdir dirname
but it doen's work, it just create a folder named date and +%Y-%m-%d.
i have tried run the command seperately in the bash prompt. after the first
sentence executed , i use $dirname to watch the value of... (4 Replies)
The objective of the code below is to create sed script to be later executed. However, it bonks because $ARCHIVENAME expands to a directory specification so the forward slashes cause problems. I can think of a few solutions that would involve redesigning the process, but I'm hoping there might be... (4 Replies)
Hi forum,
in my bash script I've many lines executing commands with redirection to log files.
...
xyz_cmd 2>&1 > $BASENAME.$LINENO
The trailing part of these lines doesn't look nice and I like to put it into a variable.
The (not working) idea is something like that
... (3 Replies)
Hello,
I use a lot this command to edit a bunch of files at once
find . -name filename" | xargs -ifoo sh -c 'echo foo ; sed "s/pattern1/pattern2/" foo > ./tmp ; mv -f ./tmp foo'
I'm trying to put a function on my .bashrc file.
function loopSed()
{
local filename=$1
local... (2 Replies)
Hello.
The file /etc/fstab contains
UUID=957c3295-9944-1593-82e2-2b90dede4312 / ext4 noatime,discard,acl,user_xattr 1 1
I fill a variable
SOME_LINE=$( cat /etc/fstab | grep \/\..*ext4 | grep noatime,discard )echo $SOME_LINE... (3 Replies)
Discussion started by: jcdole
3 Replies
LEARN ABOUT LINUX
wordexp
WORDEXP(3) Linux Programmer's Manual WORDEXP(3)NAME
wordexp, wordfree - perform word expansion like a posix-shell
SYNOPSIS
#include <wordexp.h>
int wordexp(const char *s, wordexp_t *p, int flags);
void wordfree(wordexp_t *p);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
wordexp(), wordfree(): _XOPEN_SOURCE
DESCRIPTION
The function wordexp() performs a shell-like expansion of the string s and returns the result in the structure pointed to by p. The data
type wordexp_t is a structure that at least has the fields we_wordc, we_wordv, and we_offs. The field we_wordc is a size_t that gives the
number of words in the expansion of s. The field we_wordv is a char ** that points to the array of words found. The field we_offs of type
size_t is sometimes (depending on flags, see below) used to indicate the number of initial elements in the we_wordv array that should be
filled with NULLs.
The function wordfree() frees the allocated memory again. More precisely, it does not free its argument, but it frees the array we_wordv
and the strings that points to.
The string argument
Since the expansion is the same as the expansion by the shell (see sh(1)) of the parameters to a command, the string s must not contain
characters that would be illegal in shell command parameters. In particular, there must not be any unescaped newline or |, &, ;, <, >, (,
), {, } characters outside a command substitution or parameter substitution context.
If the argument s contains a word that starts with an unquoted comment character #, then it is unspecified whether that word and all fol-
lowing words are ignored, or the # is treated as a non-comment character.
The expansion
The expansion done consists of the following stages: tilde expansion (replacing ~user by user's home directory), variable substitution
(replacing $FOO by the value of the environment variable FOO), command substitution (replacing $(command) or `command` by the output of
command), arithmetic expansion, field splitting, wildcard expansion, quote removal.
The result of expansion of special parameters ($@, $*, $#, $?, $-, $$, $!, $0) is unspecified.
Field splitting is done using the environment variable $IFS. If it is not set, the field separators are space, tab and newline.
The output array
The array we_wordv contains the words found, followed by a NULL.
The flags argument
The flag argument is a bitwise inclusive OR of the following values:
WRDE_APPEND
Append the words found to the array resulting from a previous call.
WRDE_DOOFFS
Insert we_offs initial NULLs in the array we_wordv. (These are not counted in the returned we_wordc.)
WRDE_NOCMD
Don't do command substitution.
WRDE_REUSE
The argument p resulted from a previous call to wordexp(), and wordfree() was not called. Reuse the allocated storage.
WRDE_SHOWERR
Normally during command substitution stderr is redirected to /dev/null. This flag specifies that stderr is not to be redirected.
WRDE_UNDEF
Consider it an error if an undefined shell variable is expanded.
RETURN VALUE
In case of success 0 is returned. In case of error one of the following five values is returned.
WRDE_BADCHAR
Illegal occurrence of newline or one of |, &, ;, <, >, (, ), {, }.
WRDE_BADVAL
An undefined shell variable was referenced, and the WRDE_UNDEF flag told us to consider this an error.
WRDE_CMDSUB
Command substitution occurred, and the WRDE_NOCMD flag told us to consider this an error.
WRDE_NOSPACE
Out of memory.
WRDE_SYNTAX
Shell syntax error, such as unbalanced parentheses or unmatched quotes.
VERSIONS
wordexp() and wordfree() are provided in glibc since version 2.1.
CONFORMING TO
POSIX.1-2001.
EXAMPLE
The output of the following example program is approximately that of "ls [a-c]*.c".
#include <stdio.h>
#include <stdlib.h>
#include <wordexp.h>
int
main(int argc, char **argv)
{
wordexp_t p;
char **w;
int i;
wordexp("[a-c]*.c", &p, 0);
w = p.we_wordv;
for (i = 0; i < p.we_wordc; i++)
printf("%s
", w[i]);
wordfree(&p);
exit(EXIT_SUCCESS);
}
SEE ALSO fnmatch(3), glob(3)COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
2008-07-14 WORDEXP(3)