Bash – Why Does Bash Command Fail to Run?

bash

Why does bash <command> fail to run?

$ bash date
/bin/date: /bin/date: cannot execute binary file

$ /bin/date
Fri Mar 18 05:59:24 EDT 2016

$ bash -c date
Fri Mar 18 06:00:39 EDT 2016

Best Answer

From the manual:

If arguments remain after option processing, and neither the -c nor the -s option has been supplied, the first argument is assumed to be the name of a file containing shell commands.

So bash date means "read the date file and execute the shell commands it contains". Assuming there is no date file in the current directory, bash searches the path and finds /bin/date which is a binary rather than a shell script, hence the error.

Related Solutions

Bash – Why Bash Outputs Data Instead of Executing When Script is Piped

You'll have to close (or otherwise redirect) the standard input of the individual commands:

#!/bin/bash

apt-get purge -y nginx <&-
apt-get install -y nginx <&-

date

Otherwise subsequent line are fed to the commands.

Bash – Why does “bash -x” break this script

The problem is this line:

TIMESEC=$(echo blah | ( /usr/bin/time -f %e grep blah >/dev/null ) 2>&1 | awk -F. '{print $1}')

where you are redirecting the standard error to match the standard output. bash is writing its trace-messages to the standard error, and is (for instance) using its built-in echo along with other shell constructs all in the bash process.

If you change it to something like

TIMESEC=$(echo blah | sh -c "( /usr/bin/time -f %e grep blah >/dev/null )" 2>&1 | awk -F. '{print $1}')

it will work around that problem, and perhaps be an acceptable compromise between tracing and working:

++ awk -F. '{print $1}'
++ sh -c '( /usr/bin/time -f %e grep blah >/dev/null )'
++ echo blah
+ TIMESEC=0                 
+ echo ABC--0--DEF
ABC--0--DEF
+ '[' 0 -eq 0 ']'
+ echo 'we are here!'
we are here!

Best Answer

Related Solutions

Bash – Why Bash Outputs Data Instead of Executing When Script is Piped

Bash – Why does “bash -x” break this script

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