Nested pipe output in function

Question

I am trying to make a script that will output system information using several functions that call each other. Can someone tell me what's wrong with how the piped commands' I/O is handled?

#!/bin/bash

function lyellow() {
    lyellow="$1"
    echo -e -n "\033[0;33m$lyellow"
    echo -e -n '\033[0m \n'
}


function red() {
    RED="$1"
    echo -e -n "\033[0;31m$RED"
    echo -e -n '\033[0m \n'
}

function lcyan() {
    LCYAN="$1"
    echo -e -n "\033[0;36m$LCYAN"
    echo -e -n '\033[0m \n'
}

function lgreen() {
    LGREEN="$1"
    echo -e -n "\033[1;32m$LGREEN"
    echo -e -n '\033[0m \n'
}

field ()
{
        HEADER="$1"
        SUB1="$2"
        COM1="$3"
        SUB2="$4"
        COM2="$5"
        echo -e "$(red "$(echo -e "### $HEADER ###")")"
        echo -e "$(lyellow "$(echo -e "$SUB1")")\n$(lcyan "$(echo -e "$($COM1)")")"
        echo -e "$(lyellow "$(echo -e "$SUB2")")\n$(lcyan "$(echo -e "$($COM2)")")"
}

#set -x pipefail

SEP=$(seq -s= 40|tr -d '[:digit:]')

echo $SEP
echo -e "$(lgreen "$(hostname -f) :: $(hostname -i)")"
echo $SEP

#OS
field   "Operating System" \
        "Kernel:" "/bin/uname -srp" \
        "Release:" "cat /etc/redhat-release"

echo $SEP

#DISK
field   "Storage Devices" \
        "Mounted Devices:" "mount|column -t" \
        "Disk Free:" "df -kh|column -t"

echo $SEP

#Example
lcyan "$(echo -e "$(df -kh | column -t)")"

exit 0

The output from the "#OS" "field" call works. But the "#DISK" call doesn't like the pipes to "column -t". Under "#Example" the color function calls a literal piped "column -t" fine. Here is what the output looks like:

[root@CLFT1Q ~]# sh sysinfo.sh
=======================================
CLFT1Q.local :: 10.9.19.70
=======================================
### Operating System ###
Kernel:
Linux 2.6.18-348.3.1.el5 i686
Release:
Red Hat Enterprise Linux Server release 5.9 (Tikanga)
=======================================
### Storage Devices ###
sysinfo.sh: line 36: /bin/mount|column: No such file or directory
Mounted Devices:

df: invalid option -- |
Try `df --help' for more information.
Disk Free:

=======================================
Filesystem                    Size   Used  Avail  Use%  Mounted   on
/dev/mapper/vgsystem-lv_root
3.9G                          3.3G   421M  89%    /
/dev/mapper/vgsystem-lv_var
4.9G                          2.3G   2.4G  49%    /var
/dev/mapper/vgsystem-ora
3.0G                          1008M  1.9G  36%    /ora
/dev/sda1                     99M    25M   69M    27%   /boot
tmpfs                         1014M  0     1014M  0%    /dev/shm
clnsa05:/vol/ftpnfsqa1/ftp
29G                           25G    4.2G  86%    /ftp

Please see BashFAQ/050.

Dennis Williamson
– Dennis Williamson

2013-05-10 22:15:40 +00:00
Commented May 10, 2013 at 22:15 — Dennis Williamson
– Dennis Williamson, Commented May 10, 2013 at 22:15

Barmar · Accepted Answer · 2013-05-10 21:41:35Z

1

Change "$($COM1)" to "$(eval "$COM1")", and similarly for $COM2. Variable expansions are only scanned for word splitting and wildcard expansion, not for command metacharacters like pipelines. You need to use eval to process it recursively as a command line.

answered May 10, 2013 at 21:41

Barmar

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1 Comment

gNU.be Over a year ago

You are the man. I found something about eval but wasn't sure where to try it.

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