11-05-2015
Being the first word in the line, the shell will try to execute the result of the command substitution.
Fun UNIX Fact
Quote:
Command substitution allows the output of a command to replace the command itself. Command substitution occurs when a command is enclosed as follows:
$(command)
or
`command`
Bash performs the expansion by executing command in a subshell environment and replacing the command substitution with the standard output of the command, with any trailing newlines deleted. Embedded newlines are not deleted, but they may be removed during word splitting. The command substitution $(cat file) can be replaced by the equivalent but faster $(< file).
When the old-style backquote form of substitution is used, backslash retains its literal meaning except when followed by ‘$', ‘`', or ‘\'. The first backquote not preceded by a backslash terminates the command substitution. When using the $(command) form, all characters between the parentheses make up the command; none are treated specially.
Command substitutions may be nested. To nest when using the backquoted form, escape the inner backquotes with backslashes.
If the substitution appears within double quotes, word splitting and filename expansion are not performed on the results.
9 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
Hi,All
I wrote below script(Example1.sh) and i ran but it giveing error. it's excuted yesterday.
SYSTEM_TIME=`date '+%H:%M:%S'`
CMP_LOG_TIME=`head -1 runcmp-HINET.log`
CMP_ENDED1=`grep 'HINET CMP ended' runcmp-HINET.log`
CMP_ENDED2=`echo "HINET CMP ended"`
CMP_FAILED2=`echo "HINET... (2 Replies)
Discussion started by: koti_rama
2 Replies
2. Shell Programming and Scripting
Hi,All
I wrote below script(Example1.sh) and i ran but i got error. it's excuted yesterday.
SYSTEM_TIME=`date '+%H:%M:%S'`
CMP_LOG_TIME=`head -1 runcmp-HINET.log`
CMP_ENDED1=`grep 'HINET CMP ended' runcmp-HINET.log`
CMP_ENDED2=`echo "HINET CMP ended"`
CMP_FAILED2=`echo "HINET CMP... (2 Replies)
Discussion started by: koti_rama
2 Replies
3. Shell Programming and Scripting
Hi All,
I am trying to run a script to FTP files from one UNIX server to another UNIX server. Actually I can able to FTP file successfully by manually or paste whole script at prompt. But when I am trying to run script it is giving error.
Please let me know the cause.
#!/bin/sh... (3 Replies)
Discussion started by: nz80qy
3 Replies
4. Shell Programming and Scripting
I found error 138 while run a shell script.
Please tell me what it's mean?? and how can i prevent that error.
Thanks in advance..... (1 Reply)
Discussion started by: rinku
1 Replies
5. Shell Programming and Scripting
i am having a weird error on mac os x running some shell scripts. i am a complete newbie at this and this question concerns 2 scripts. one of which a friend of mine wrote (videochecker.sh) a couple weeks ago and it's been running fine on another machine.
then last week i wrote capture.sh and it... (2 Replies)
Discussion started by: danpaluska
2 Replies
6. UNIX for Dummies Questions & Answers
How to use Mailx command in unix shell script, its throwing below error
#!/bin/ksh
let x=3
If ; then
mailx -s “ $x is greater than 2” example@gmail.com << EOF
This is the message body
EOF
fi
its throwing error as syntax error at EOF... (10 Replies)
Discussion started by: only4satish
10 Replies
7. Shell Programming and Scripting
I am trying to run a unix script in my home directory.Snippet below
echo "`date '+%Y%m%d_%H%M%S'` Getting ProductList.dat"
if ( -f $DIR/ProductList.dat) then
cp $DIR/ProductList.dat MigratedProductList.dat
else
echo "`date '+%Y%m%d_%H%M%S'`ProductList.dat does not exist; Processing... (4 Replies)
Discussion started by: Mary James
4 Replies
8. Shell Programming and Scripting
hi guys can you please help me i have the following script to load to a database but when i execute it...its saying Check_Process: not found
#!/bin/ksh
##-To load Oracle user profile
##./monitor_io.ksh
##./test.ksh
SCP_DIR=/export/home/yani_m/scripts
... (9 Replies)
Discussion started by: LucyYani
9 Replies
9. Shell Programming and Scripting
Hi ,
I am a newbie to shell scripting. I am getting the error on AIX machine
/tadfdc_setup_fed.sh: +: not found
Here tadfdc_setup_fed.sh is script which works fine on Linux Machine. But gives error on AIX (1 Reply)
Discussion started by: Anupam Kakade
1 Replies
LEARN ABOUT SUSE
platform::shell
platform::shell(n) Tcl Bundled Packages platform::shell(n)
__________________________________________________________________________________________________________________________________________________
NAME
platform::shell - System identification support code and utilities
SYNOPSIS
package require platform::shell ?1.1.4?
platform::shell::generic shell
platform::shell::identify shell
platform::shell::platform shell
_________________________________________________________________
DESCRIPTION
The platform::shell package provides several utility commands useful for the identification of the architecture of a specific Tcl shell.
This package allows the identification of the architecture of a specific Tcl shell different from the shell running the package. The only
requirement is that the other shell (identified by its path), is actually executable on the current machine.
While for most platform this means that the architecture of the interrogated shell is identical to the architecture of the running shell
this is not generally true. A counter example are all platforms which have 32 and 64 bit variants and where a 64bit system is able to run
32bit code. For these running and interrogated shell may have different 32/64 bit settings and thus different identifiers.
For applications like a code repository it is important to identify the architecture of the shell which will actually run the installed
packages, versus the architecture of the shell running the repository software.
COMMANDS
platform::shell::identify shell
This command does the same identification as platform::identify, for the specified Tcl shell, in contrast to the running shell.
platform::shell::generic shell
This command does the same identification as platform::generic, for the specified Tcl shell, in contrast to the running shell.
platform::shell::platform shell
This command returns the contents of tcl_platform(platform) for the specified Tcl shell.
KEYWORDS
operating system, cpu architecture, platform, architecture
platform::shell 1.1.4 platform::shell(n)