Login or Register to Ask a Question and Join Our Community


Shell Programming and Scripting

Bash Parameter Expansion

Login to Discuss or Reply to this Discussion in Our Community

 
Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Bash Parameter Expansion
# 1  
Old 02-24-2018
Bash Parameter Expansion
I have made the following examples that print various parameter expansions

Code:
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
(text##*.): sac
(text##*/): iv.hpac..hhz.d.2016.250.070018.sac

Is there a way to get the filename without the directory and without the extension,
using parameter expansion to get

Code:
  iv.hpac..hhz.d.2016.250.070018

---------- Post updated at 02:59 PM ---------- Previous update was at 02:41 PM ----------

The following does not work for example

Code:
${${text##*/}%.*}

# 2  
Old 02-24-2018
You have already shown us that you know how to get what you want:
Code:
text="iv-hhz-sac/hpac/hhz.d/iv.hpac..hhz.d.2016.250.070018.sac"
result=${text%.*}
result=${result##*/}
printf '%s\n' "$result"

which, as requested, produces the output:
Code:
iv.hpac..hhz.d.2016.250.070018

This User Gave Thanks to Don Cragun For This Post:
kristinu
# 3  
Old 02-24-2018
Quote:
Originally Posted by kristinu
Is there a way to get the filename without the directory and without the extension, using parameter expansion to get

Code:
  iv.hpac..hhz.d.2016.250.070018

Yes, but it would be cumbersome and plain ugly. Writing scripts (i suppose you need it in a script) is all about clarity and making it easy to understand what is done, therefore you should do it in two steps using the expansions you already found. I would write it like this:

Code:
text="${text##*/}"      # cut off the path
text="${text%.*}"       # cut off the extension

For completeness' (but again: don't really do it! This is just to show off my prowess in writing incomprehensible code! ;-) ) sake: you can use an expansion inside another expansion as a pattern. For instance, this cuts off the first character in a string, notice the nested expansion:

Code:
chLine="abcdefghi"

while [ -n "$chLine" ] ; do
     chChar="${chLine%${chLine#?}}"        # nested expansion!!
     chLine="${chLine#?}"

     echo char is: \"$chChar\"
     echo line is: \"$chLine\"
done

Using this device you could do what you want. Don't!

I hope this helps.

bakunin
These 2 Users Gave Thanks to bakunin For This Post:
apmcd47 kristinu
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Use parameter expansion over a parameter expansion in bash.

Hello All, Could you please do help me here as I would like to perform parameter expansion in shell over a parameter expansion. Let's say I have following variable. path="/var/talend/nat/cdc" Now to get only nat I could do following. path1="${path%/*}" path1="${path1##*/}" Here... (8 Replies)
Discussion started by: RavinderSingh13
8 Replies

2. 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

3. 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

4. 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

5. Shell Programming and Scripting

Bash expansion

Hello. I cannot write a command without using eval. Any help is welcome Note 1 : What does the function SOMETHING has no importance. Note 2 : What does the command find has no importance. It is an expansion variable problem : where to put or or or anythings else What works (FILTRE_1... (8 Replies)
Discussion started by: jcdole
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

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

8. 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

9. 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

10. 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
Login or Register to Ask a Question