Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: How to understand special character for line reading in bash shell?
Top Forums Shell Programming and Scripting How to understand special character for line reading in bash shell? Post 303039063 by RudiC on Saturday 21st of September 2019 02:24:23 PM
Old 09-21-2019
Not sure I'm an expert nor a guru, but this is what I'd do: refer to the respective man pages.
man bash:
Quote:
Parameter Expansion

${parameter#word}
${parameter##word}
Remove matching prefix pattern.


${parameter%word}
${parameter%%word}
Remove matching suffix pattern.



CONDITIONAL EXPRESSIONS.



An additional binary operator, =~, is available, with the same precedence as == and !=. When it is used, the string to the right of the operator is considered a POSIX extended regular expression and matched accordingly (as in regex(3))
Of course you need to learn the difference between shell's pattern matching and regex matching.

man regex:
Quote:
An atom is a regular expression ... '^' (matching the null string at the beginning of a line)

A bracket expression is a list of characters enclosed in "[]". It normally matches any single character from the list (but see below). If the list begins with '^', it matches any single character (but see below) not from the rest of the list.
Admittedly the ambiguous use of the caret is something you need to accustom to.
These 2 Users Gave Thanks to RudiC For This Post:
drl duke0001
 

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

[OpenServer 5]Line Printing and special character (é @)

Hello, On Sco OpenServer 5, i want to print using the lpr command, no CUPS installed. I print on an HP LaserJet 4050 on LAN (IP 192.168.x.x) the printer is installed by HP Network Printer service. it works fine, but Specials characters, like é, @ or ° print bad characters. Is there... (5 Replies)
Discussion started by: tankd
5 Replies

2. Shell Programming and Scripting

bash shell: 'exec', 'eval', 'source' - looking for help to understand

Hi, experts. Whould anybody clear explay me difference and usage of these 3 commands (particulary in bash) : exec eval source I've tryed to read the manual pages but did not get much. Also could not get something useful from Google search - just so much and so not exactly, that is... (3 Replies)
Discussion started by: alex_5161
3 Replies

3. Shell Programming and Scripting

Adding a special character at the end of the line

I used following to add * at the end of the line in file1. It adds * at the end but has a space before it for some lines but some other lines it adds exactly after the last character. How do I take out the space ? sed 's/$/*/' file1 > file2 example: contents of file1 : ... (2 Replies)
Discussion started by: pitagi
2 Replies

4. Shell Programming and Scripting

How to insert a character in line in Special condition?

Hi, I have a log file generated by a tool which has the following look : /tmp/releases/directory/datefilename1_release_date.zip /tmp/releases/directory/datefilename2_release_date.zip /tmp/releases/directory/datefilename3_release_date.zip... (8 Replies)
Discussion started by: bhaskar_m
8 Replies

5. Shell Programming and Scripting

I need to understand the differences between the bash shell and the Bourne shell

I do not claim to be an expert, but I have done things with scripts that whole teams of folks have said can not be done. Of course they should have said we do not have the intestinal fortitude to git-r-done. I have been using UNIX actually HPUX since 1992. Unfortunately my old computer died and... (7 Replies)
Discussion started by: awk_sed_hello
7 Replies

6. Shell Programming and Scripting

Printing special character in bash

I am using this character as a delimiter 'þ' Currently, I set it straight: DELIMITER='þ' However, while copying the file, this character often gets mangled. Is there a bash way (perhaps using tr or printf) of generating this character. It corresponds to "chr(0xfe)" if using perl. (I've... (6 Replies)
Discussion started by: sentinel
6 Replies

7. Shell Programming and Scripting

parse special character in the line

Hi all, I have a file with some module names as below. Font::AFM Data::Grove ---> libxml-perl Net::LDAP ---> perl-ldap DBI XML .... ... .... and so on ... The file has some lines with the character " -->" . Now how can I cut only the last column of the line wherever "-->" is... (4 Replies)
Discussion started by: vijaya2006
4 Replies

8. UNIX for Dummies Questions & Answers

Reading character by character - BASH

Hello every one and thanks in advance for the time you will take to think about my problem. I would like to know if it's possible (in BASH) to read a text file character after character. Exactly this is what I would like to do : Txt file : ATGCAGTTCATTGCCAAA...... (~2.5 millions... (3 Replies)
Discussion started by: sluvah
3 Replies

9. Shell Programming and Scripting

Shell script question in special character

when I execute the unix commands its works normally in the 1st part. When I the tried the same in shell scripting the directory is not displayed in 2nd part example. please let me know what needs to be done. Unix : client=~zsvdbs echo $client /shome/zsvhome/zsvdbs Using... (3 Replies)
Discussion started by: keerthi2016
3 Replies

10. UNIX for Beginners Questions & Answers

Escape bash-special character in a bash string

Hi, I am new in bash scripting. In my work, I provide support to several users and when I connect to their computers I use the same admin and password, so I am trying to create a script that will only ask me for the IP address and then connect to the computer without having me to type the user... (5 Replies)
Discussion started by: arcoa05
5 Replies

LEARN ABOUT OPENSOLARIS

shells

shells(4)							   File Formats 							 shells(4)

NAME

       shells - shell database

SYNOPSIS

       /etc/shells

DESCRIPTION

       The shells file contains a list of the shells on the system. Applications use this file to determine whether a shell is valid. See getuser-
       shell(3C). For each shell a single line should be present, consisting of the shell's path, relative to root.

       A hash mark (#) indicates the beginning of a comment; subsequent characters up to the end of the line are not interpreted by  the  routines
       which search the file. Blank lines are also ignored.

       The following default shells are used by utilities: /bin/bash, /bin/csh, /bin/jsh, /bin/ksh, /bin/ksh93, /bin/pfcsh, /bin/pfksh, /bin/pfsh,
       /bin/sh, /bin/tcsh, /bin/zsh, /sbin/jsh, /sbin/sh, /usr/bin/bash, /usr/bin/csh, /usr/bin/jsh, /usr/bin/ksh, /usr/bin/ksh93, /usr/bin/pfcsh,
       /usr/bin/pfksh, /usr/bin/pfsh, and /usr/bin/sh, /usr/bin/tcsh, /usr/bin/zsh, and /usr/sfw/bin/zsh. /etc/shells overrides the default list.

       Invalid shells in /etc/shells could cause unexpected behavior, such as being unable to log in by way of ftp(1).

FILES

       /etc/shells    list of shells on system

SEE ALSO

       vipw(1B), ftpd(1M), sendmail(1M), getusershell(3C), aliases(4)

SunOS 5.11							    20 Nov 2007 							 shells(4)
All times are GMT -4. The time now is 10:42 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy