36 lines
1,012 B
Bash
Executable file
36 lines
1,012 B
Bash
Executable file
#!/usr/bin/env bash
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#
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# bash /dev/tcp redirection to check Internet connection
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#
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# SPDX-License-Identifier: MIT
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TCP_HOST=example.com # A given website
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TCP_PORT=80 # Port 80 is http
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# Try to connect. (Somewhat similar to a 'ping' . . .)
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echo "HEAD / HTTP/1.0" >/dev/tcp/${TCP_HOST}/${TCP_PORT}
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MYEXIT=$?
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: <<EXPLANATION
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If bash was compiled with --enable-net-redirections, it has the capability of
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using a special character device for both TCP and UDP redirections. These
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redirections are used identically as STDIN/STDOUT/STDERR. The device entries
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are 30,36 for /dev/tcp:
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mknod /dev/tcp c 30 36
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>From the bash reference:
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/dev/tcp/host/port
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If host is a valid hostname or Internet address, and port is an integer
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port number or service name, Bash attempts to open a TCP connection to the
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corresponding socket.
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EXPLANATION
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if [ "X$MYEXIT" = "X0" ]; then
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echo "Connection successful. Exit code: $MYEXIT"
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else
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echo "Connection unsuccessful. Exit code: $MYEXIT"
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fi
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exit $MYEXIT
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