Sponsored Content
Top Forums Shell Programming and Scripting Use parameter expansion over a parameter expansion in bash. Post 303043417 by wisecracker on Tuesday 28th of January 2020 10:53:10 AM
Old 01-28-2020
Hi nez...
I do not like 'eval' but here goes and is also 'dash' compliant...
Code:
Last login: Tue Jan 28 14:17:35 on ttys000
AMIGA:amiga~> dash
AMIGA:\u\w> path="/var/talend/nat/cdc"
AMIGA:\u\w> path=$( eval path=${path%/*} && echo ${_##*/} )
AMIGA:\u\w> echo "${path}"
nat
AMIGA:\u\w> exit
AMIGA:amiga~> _

 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

removing html tags via parameter expansion

Hi all- I have a variable that contains a web page: echo $STUFF <html> <head> <title>my page</title></head> <body> blah blah etc.. Can I use the shell's parameter expansion abilities to remove just the tags? I thought that FIXHTML=${STUFF//<*>/} might do it, but it didn't seem to... (2 Replies)
Discussion started by: rev66
2 Replies

2. Shell Programming and Scripting

Need to print the expansion of the found string (the expansion is beween two delimiters '-' , '||'

Hi , could anyone help me out with this problem. sample.txt has this content : u001- this is used for project1 || u002- this is used for p2|| not to be printed u003- this is used for project3 || u004- this is used for p4 || u005- this is used for project5 || u006- this is used for p6... (9 Replies)
Discussion started by: Balaji PK
9 Replies

3. Shell Programming and Scripting

Need help with parameter expansion

Say you have this numeric variable that can be set by the user but you never want it to leave a certain range when it gets printed. How could you use parameter expansion such that it will never expand outside of that boundary? Thanks ---------- Post updated at 11:09 PM ---------- Previous update... (3 Replies)
Discussion started by: stevenswj
3 Replies

4. Shell Programming and Scripting

Bash parameter expansion from a config file

Hi - I am trying to do a simple config file with known variable names in it, e.g.: contents of config file a.conf: -a -b $work -c $host simplified contents of bash script file: work='trunk' host='alaska' opts=$(tr '\n' ' ' < a.conf) opts="$opts $*" mycommand $opts arg1 arg2 The... (3 Replies)
Discussion started by: mrengert
3 Replies

5. Shell Programming and Scripting

Parameter expansion not working for all strings...

I'm trying to write a script that parses my music collection and hard link some filenames that my media player doesn't like to other names. To do this I need to extract the name and remove alla non ASCII characters from that and do a cp -l with the result. Problem is this: 22:16:58 $... (8 Replies)
Discussion started by: refuser
8 Replies

6. UNIX for Dummies Questions & Answers

Parameter Expansion with regular expression

Hello experts, I am exploring parameter expansion, and trying to cut the fields in a URL. Following is the requirement: I have // abc.nnt /dir1/dir2/dir3/dir4/somefile.java What i need to get is the path after dir3, and dir3 will be passed. output that i need is... (1 Reply)
Discussion started by: gjarms
1 Replies

7. Shell Programming and Scripting

Bash Parameter Expansion

I have made the following examples that print various parameter expansions text: iv-hhz-sac/hpac/hhz.d/iv.hpac..hhz.d.2016.250.070018.sac (text%.*): iv-hhz-sac/hpac/hhz.d/iv.hpac..hhz.d.2016.250.070018 (text%%.*): iv-hhz-sac/hpac/hhz (text#*.): d/iv.hpac..hhz.d.2016.250.070018.sac... (2 Replies)
Discussion started by: kristinu
2 Replies

8. Shell Programming and Scripting

Bash Parameter Expansion

#!/bin/bash SNMPW='/usr/bin/snmpwalk' while read h i do loc=$($SNMPW -v3 -u 'Myusername' -l authPriv -a SHA -A 'Password1' -x AES -X 'Password2' $i sysLocation.0 2>/dev/null) loc=${loc:-" is not snmpable."} loc=${loc##*: } loc=${loc//,/} echo "$i,$h,$loc" done < $1 My question is ... ... (1 Reply)
Discussion started by: sumguy
1 Replies

9. Shell Programming and Scripting

Bash : More parameter expansion and IFS

I am trying to become more fluent with the interworking of bash and minimize the number of external calls. Sample Data. This will be the response of the snmp query. SNMPv2-MIB::sysName.0 = STRING: SomeHostName SNMPv2-MIB::sysObjectID.0 = OID: SNMPv2-SMI::enterprises.9.1.1745... (5 Replies)
Discussion started by: sumguy
5 Replies

10. Shell Programming and Scripting

Bash : Parameter expansion ${var:-file*}

Example data $ ls *somehost* 10.10.10.10_somehost1.xyz.com.log 11.11.11.11_somehost2.xyz.com.log #!/bin/bash #FILES="*.log" FILES=${FILES:-*.log} for x in $FILES do ip="${x%%_*}" # isolate IP address x="${x##*_}" # isolate hostname hnam="${x%.*}" # Remove the ".log"... (2 Replies)
Discussion started by: popeye
2 Replies
wordexp(3)						     Library Functions Manual							wordexp(3)

NAME
wordexp, wordfree - Perform word expansions LIBRARY
Standard C Library (libc.so, libc.a) SYNOPSIS
#include <wordexp.h> int wordexp( const char *words, wordexp_t *pwordexp, int flags); void wordfree( wordexp_t *pwordexp); STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: wordexp(), wordfree(): XPG4, XPG4-UNIX Refer to the standards(5) reference page for more information about industry standards and associated tags. PARAMETERS
Specifies the string containing the tokens to be expanded. Contains a pointer to a wordexp_t structure. Contains a bit flag specifying the configurable aspects of the wordexp() function. DESCRIPTION
The wordexp() function performs word expansions equivalent to the word expansion that would be performed by the shell if the contents of the words parameter were arguments on the command line. The list of expanded words are placed in the pwordexp parameter. The expansions are the same as that which would be performed by the shell if the words parameter were the part of a command line represent- ing the parameters to a command. Therefore, the words parameter cannot contain an unquoted newline character or any of the unquoted shell special characters: | & ; < > except in the case of command substitution. The words parameter also cannot contain unquoted parentheses or braces, except in the case of command or variable substitution. If the words parameter contains an unquoted comment character (#) that is the beginning of a token, the wordexp() function may treat the comment character as a regular character, or may interpret it as a comment indicator and ignore the remainder of the expression in the words parameter. The wordexp() function stores the number of generated words and a pointer to a list of pointers to words in the pwordexp parameter. Each individual field created during the field splitting or pathname expansion is a separate word in the list specified by the pwordexp parame- ter. The first pointer after the last token in the list is a null pointer. The expansion of special parameters *, @, #, ?, -, $, !, and 0 is unspecified. The words are expanded in the following order: Tilde expansion is performed first. Parameter expansion, command substitu- tion, and arithmetic expansion are performed next, from beginning to end. Field splitting is then performed on fields generated by step 2, unless the IFS (Input Field Separators) is full. Pathname expansion is performed, unless the set -f command is in effect. Quote removal is always performed last. The pwordexp structure is allocated by the caller, but memory to contain the expanded tokens is allocated by the wordexp() function and added to the structure as needed. The wordfree() function frees any memory associated with pwordexp() from a previous call to wordexp(). The value of the flags parameter is the bitwise inclusive OR of the following constants, which are defined in the wordexp.h file: Appends words generated to those generated by a previous call to the wordexp() function. Makes use of the we_offs structure. If the WRDE_DOOFFS flag is set, the we_offs structure is used to specify the number of null pointers to add to the beginning of the we_words structure. If the WRDE_DOOFFS flag is not set in the first call to the wordexp() function with the pwordexp parameter, it should not be set in subsequent calls to the wordexp() function with the pwordexp parameter. Fails if command substitution is requested. The pwordexp parameter was passed to a previous successful call to the wordexp() function. Therefore, the memory previously allocated may be reused. Does not redi- rect standard error to /dev/null. Reports error on an attempt to expand an undefined shell variable. The WRDE_APPEND flag can be used to append a new set of words to those generated by a previous call to the wordexp() function. The follow- ing rules apply when two or more calls to the wordexp() function are made with the same value of the pwordexp parameter and without inter- vening calls to the wordfree() function: The first such call does not set the WRDE_APPEND flag. All subsequent calls set it. For a single invocation of the wordexp() function, all calls either set the WRDE_DOOFFS flag, or do not set it. After the second and each subsequent call, the pwordexp parameter points to a list containing the following: Zero or more null characters, as specified by the WRDE_DOOFFS flag and the we_offs field of the wordexp_t structure. Pointers to the words that were in the pwordexp parameter before the call, in the same order as before. Pointers to the new words generated by the latest call, in the specified order. The count returned in the pwordexp parameter is the total number of words from all of the calls. The application should not modify the pwordexp parameter between the calls. Unless the WRDE_SHOWERR flag is set in the flags parameter, the wordexp() function redirects standard error to /dev/null for any utilities executed as a result of command substitution while expanding the words parameter. If the WRDE_SHOWERR flag is set, the wordexp() function can write messages to standard error if syntax errors are detected while expanding the words parameter. If any of the following conditions occurs, the wordexp() function returns the corresponding nonzero constant, which is defined in the word- exp.h file. One of the unquoted characters |, & , ;, <, >, newline, parenthesis, or braces appears in the words parameter in an inappro- priate context. Reference to undefined shell variable when the WRDE_UNDEF flag is set in the flags parameter. Command substitution requested when the WRDE_NOCMD flag is set in the flags parameter. An attempt to allocate memory was unsuccessful. Shell syntax error, such as unbalanced parentheses or unterminated string. The wordexp() function allows an application to perform all of the shell's expansions on a word or words obtained from a user. For example, if the application prompts for a filename (or a list of file names) and then uses the wordexp() function to process the input, the user could respond with anything that would be valid as input to the shell. The WRDE_NOCMD flag is provided for applications that, for security or other reasons, want to prevent a user from executing shell commands. Disallowing unquoted shell special characters also prevents unwanted side effects such as executing a command or writing to a file. NOTES
The wordexp() function can cause a signal to be issued. If a user program catches the signal, wordexp() may return an error. FILES
Defines word expansion macros, data types, and functions. RETURN VALUES
If no errors are encountered while expanding the words parameter, the wordexp() function returns a value of 0 (zero). If an error occurs, the function returns a nonzero value indicating the error. If the wordexp() function returns the error value WRDE_NOSPACE, then the expression in the pwordexp parameter is updated to reflect any words that were successfully expanded. In other cases, the pwordexp parameter is not modified. The wordfree() function returns no value. RELATED INFORMATION
Functions: glob(3) Standards: standards(5) delim off wordexp(3)
All times are GMT -4. The time now is 09:01 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy