user2915: How can I take the output of sha256sum
sudofox@ubuntu:~$ echo -n 'Hi guys!' | sha256sum
7542fb6685f9fd8f37d56faf62f0bb4563684a51539e4b26f0840db361e0027c  -

and turn it into a Base58Check encoded private key?
I need to be able to do this with a list of SHA256 keys. Is there a script I can download, or must I spend a few weeks making it just so I can make my temporary addresses?
In response to first comment: 
No, I must input a string, like "fluttershy", for example, into sha256sum and then I must encode the output of sha256sum into a base58check private key.
string -->sha256sum --> some automagic process, which is the purpose of this question --> bitcoin private key.
Update: For anyone wanting to use Grondilu's Bitcoin Bash Tools: You need to source the bitcoin.sh file after extracting it into your directory to use the functions.
source ./bitcoin.sh
Update 2 (Aug 2017): Rewrote script to go from step 1 to WIF in one go. You can just add the declaration of base58 and the encodeBase58 functions from bitcoin.sh if you want to skip the rest of the lib.
#!/bin/bash
#Tool to convert bitcoin privkeys into WIF keys
# by sudofox

source ./bitcoin.sh

KEY=$1 # first arg

# add 0x80 to beginning
EXTENDEDKEY=$(echo 80$KEY)
FIRSTHASH=$(echo -n "$EXTENDEDKEY" |xxd -r -p |sha256sum -b|awk '{print $1}')
SECONDHASH=$(echo -n "$FIRSTHASH" |xxd -r -p |sha256sum -b|awk '{print $1}')
CHECKSUM=$(echo $SECONDHASH|cut -c1-8)
FINAL=$(encodeBase58 $EXTENDEDKEY$CHECKSUM)
echo $FINAL

The usage would be 
./sha256_to_privkey.sh key
where in my example (see Stephen Gornick's answer), key would be
807542FB6685F9FD8F37D56FAF62F0BB4563684A51539E4B26F0840DB361E0027CCD5C4A8E

Do the same thing for the various functions, modifying as needed. Hope this helps anyone struggling to use the tools.

user35880: If you don't want to compute the key manually, there's a useful command-line utility for this called bitcoin-tool:
$ ./bitcoin-tool \
  --input-file <(echo -n 'Hi guys!' | openssl dgst -sha256 -binary) \
  --input-format raw \
  --input-type private-key \
  --network bitcoin \
  --output-type private-key-wif \
  --output-format base58check \
  --public-key-compression uncompressed
5JhvsapkHeHjy2FiUQYwXh1d74evuMd3rGcKGnifCdFR5G8e6nH

Passing --output-type all yields even more interesting output:
address.hex:00a25b865343d3fcc08994005f496265b48349e363
address.base58:13GC5PkewvCycNNVVUuwJEnxPr6Lz
address.base58check:1FoU7KqP2xnWBo7sULZn5EynWdbYVVBXaG
public-key-ripemd160.hex:a25b865343d3fcc08994005f496265b48349e363
public-key-ripemd160.base58:3GC5PkewvCycNNVVUuwJEnxPr6Lz
public-key-ripemd160.base58check:FoU7KqP2xnWBo7sULZn5EynWdbYSDL49B
public-key-sha256.hex:12317a311bea88a372138319d2ab671ef9fed4ada741d91f368a4c6c7b3c146a
public-key-sha256.base58:2E26bn7S3ByBj1KWn8zjTVzAYVRD5osYmo1HAP5UfAPB
public-key-sha256.base58check:91iv7C9DcPrrReTtBJsxMTRFHKm2yJwsYkz1mbDk51ePCC54y
public-key.hex:048c6d8595550811bef5592e56f33f306cd07561b3f65ab10d9188fc0aa89aba7a564aa08b528475baadf0a0035633894248269f266c3c71b67e574dd368275c1c
public-key.base58:QHH5Zy6u7FsTPjLdMLp4yVdL6cFYo2yh8XoptynaU8HEqheCNEwJiVCfCpm6BBBuCXVB2ESny8qAAEQN3Efc1kq1
public-key.base58check:3dLjoxm8unYpP6iKX95T5YWXVA7xbVhmyJrnKoWYjeTFWqKTmgVoUSyjXd1D5KWNnzYgcGw5fn8WefUjnTDnXBVrTtkTGE
private-key-wif.hex:807542fb6685f9fd8f37d56faf62f0bb4563684a51539e4b26f0840db361e0027c
private-key-wif.base58:fAHHP3kbUP5cDBoAfwrZYCR4WC6BnnQCEaQPMaNdrRyCF
private-key-wif.base58check:5JhvsapkHeHjy2FiUQYwXh1d74evuMd3rGcKGnifCdFR5G8e6nH
private-key.hex:7542fb6685f9fd8f37d56faf62f0bb4563684a51539e4b26f0840db361e0027c
private-key.base58:8tjwWnNgm3DrBEwCsPqbSAPkCspRRmA8ftHjQTycL3gw
private-key.base58check:teHuNfDBiki1sSSD73SeGVtTq1hDky8TYY3cfuxkPmuftixzQ


user153: What you are requesting is described as computing the Wallet Import Format for that private key:

http://en.bitcoin.it/wiki/Wallet_import_format

Using your example:
1.) Take a private key (Below is the HEX representation of binary value)

7542FB6685F9FD8F37D56FAF62F0BB4563684A51539E4B26F0840DB361E0027C

2.) Add a 0x80 byte in front of it

807542FB6685F9FD8F37D56FAF62F0BB4563684A51539E4B26F0840DB361E0027C

3.) Perform SHA-256 hash on the extended key
$ echo -n '807542FB6685F9FD8F37D56FAF62F0BB4563684A51539E4B26F0840DB361E0027C' | xxd -r -p | sha256sum -b


7DE4708EB23AB611371BB778FC0C8BDE80394AB2D8704D7129FB5771E2F1730D

4.) Perform SHA-256 hash on result of SHA-256 hash
$ echo -n '7DE4708EB23AB611371BB778FC0C8BDE80394AB2D8704D7129FB5771E2F1730D' | xxd -r -p | sha256sum -b


CD5C4A8E03DFBB0E3AA021C2D74A9EAA43CE4C9CB1B20FC88729A7A5834141CA

5.) Take the first 4 bytes of the second SHA-256 hash, this is the checksum

CD5C4A8E

6.) Add the 4 checksum bytes from point 5 at the end of the extended key from point 2

807542FB6685F9FD8F37D56FAF62F0BB4563684A51539E4B26F0840DB361E0027CCD5C4A8E

7.) Convert the result from a byte string into Base58 to get it into the Base58Check format. This is also known as the Wallet Import Format
(Converted from point 6 to base58 using https://bitcointools.appspot.com, or using encodeBase58 from https://github.com/grondilu/bitcoin-bash-tools)

5JhvsapkHeHjy2FiUQYwXh1d74evuMd3rGcKGnifCdFR5G8e6nH


2915: <p>How can I take the output of sha256sum</p>

<pre><code>sudofox@ubuntu:~$ echo -n 'Hi guys!' | sha256sum
7542fb6685f9fd8f37d56faf62f0bb4563684a51539e4b26f0840db361e0027c  -
</code></pre>

<p>and turn it into a Base58Check encoded private key?</p>

<p>I need to be able to do this with a list of SHA256 keys. Is there a script I can download, or must I spend a few weeks making it just so I can make my temporary addresses?</p>

<p>In response to first comment: 
No, I must input a string, like "fluttershy", for example, into sha256sum and then I must encode the output of sha256sum into a base58check private key.</p>

<p>string -->sha256sum --> some automagic process, which is the purpose of this question --> bitcoin private key.</p>

<p>Update: For anyone wanting to use Grondilu's Bitcoin Bash Tools: You need to source the bitcoin.sh file after extracting it into your directory to use the functions.</p>

<p><code>source ./bitcoin.sh</code></p>

<p>Update 2 (Aug 2017): Rewrote script to go from step 1 to WIF in one go. You can just add the declaration of base58 and the encodeBase58 functions from bitcoin.sh if you want to skip the rest of the lib.</p>

<pre><code>#!/bin/bash
#Tool to convert bitcoin privkeys into WIF keys
# by sudofox

source ./bitcoin.sh

KEY=$1 # first arg

# add 0x80 to beginning
EXTENDEDKEY=$(echo 80$KEY)
FIRSTHASH=$(echo -n "$EXTENDEDKEY" |xxd -r -p |sha256sum -b|awk '{print $1}')
SECONDHASH=$(echo -n "$FIRSTHASH" |xxd -r -p |sha256sum -b|awk '{print $1}')
CHECKSUM=$(echo $SECONDHASH|cut -c1-8)
FINAL=$(encodeBase58 $EXTENDEDKEY$CHECKSUM)
echo $FINAL
</code></pre>

<p>The usage would be </p>

<p>./sha256_to_privkey.sh key</p>

<p>where in my example (see Stephen Gornick's answer), key would be</p>

<pre><code>807542FB6685F9FD8F37D56FAF62F0BB4563684A51539E4B26F0840DB361E0027CCD5C4A8E
</code></pre>

<p>Do the same thing for the various functions, modifying as needed. Hope this helps anyone struggling to use the tools.</p>
 35880: <p>If you don't want to compute the key manually, there's a useful command-line utility for this called <a href="https://github.com/matja/bitcoin-tool" rel="noreferrer"><code>bitcoin-tool</code></a>:</p>

<pre><code>$ ./bitcoin-tool \
  --input-file &lt;(echo -n 'Hi guys!' | openssl dgst -sha256 -binary) \
  --input-format raw \
  --input-type private-key \
  --network bitcoin \
  --output-type private-key-wif \
  --output-format base58check \
  --public-key-compression uncompressed
5JhvsapkHeHjy2FiUQYwXh1d74evuMd3rGcKGnifCdFR5G8e6nH
</code></pre>

<p>Passing <code>--output-type all</code> yields even more interesting output:</p>

<pre><code>address.hex:00a25b865343d3fcc08994005f496265b48349e363
address.base58:13GC5PkewvCycNNVVUuwJEnxPr6Lz
address.base58check:1FoU7KqP2xnWBo7sULZn5EynWdbYVVBXaG
public-key-ripemd160.hex:a25b865343d3fcc08994005f496265b48349e363
public-key-ripemd160.base58:3GC5PkewvCycNNVVUuwJEnxPr6Lz
public-key-ripemd160.base58check:FoU7KqP2xnWBo7sULZn5EynWdbYSDL49B
public-key-sha256.hex:12317a311bea88a372138319d2ab671ef9fed4ada741d91f368a4c6c7b3c146a
public-key-sha256.base58:2E26bn7S3ByBj1KWn8zjTVzAYVRD5osYmo1HAP5UfAPB
public-key-sha256.base58check:91iv7C9DcPrrReTtBJsxMTRFHKm2yJwsYkz1mbDk51ePCC54y
public-key.hex:048c6d8595550811bef5592e56f33f306cd07561b3f65ab10d9188fc0aa89aba7a564aa08b528475baadf0a0035633894248269f266c3c71b67e574dd368275c1c
public-key.base58:QHH5Zy6u7FsTPjLdMLp4yVdL6cFYo2yh8XoptynaU8HEqheCNEwJiVCfCpm6BBBuCXVB2ESny8qAAEQN3Efc1kq1
public-key.base58check:3dLjoxm8unYpP6iKX95T5YWXVA7xbVhmyJrnKoWYjeTFWqKTmgVoUSyjXd1D5KWNnzYgcGw5fn8WefUjnTDnXBVrTtkTGE
private-key-wif.hex:807542fb6685f9fd8f37d56faf62f0bb4563684a51539e4b26f0840db361e0027c
private-key-wif.base58:fAHHP3kbUP5cDBoAfwrZYCR4WC6BnnQCEaQPMaNdrRyCF
private-key-wif.base58check:5JhvsapkHeHjy2FiUQYwXh1d74evuMd3rGcKGnifCdFR5G8e6nH
private-key.hex:7542fb6685f9fd8f37d56faf62f0bb4563684a51539e4b26f0840db361e0027c
private-key.base58:8tjwWnNgm3DrBEwCsPqbSAPkCspRRmA8ftHjQTycL3gw
private-key.base58check:teHuNfDBiki1sSSD73SeGVtTq1hDky8TYY3cfuxkPmuftixzQ
</code></pre>
 153: <p>What you are requesting is described as computing the Wallet Import Format for that private key:</p>

<ul>
<li><a href="http://en.bitcoin.it/wiki/Wallet_import_format" rel="noreferrer">http://en.bitcoin.it/wiki/Wallet_import_format</a></li>
</ul>

<p>Using your example:</p>

<p>1.) Take a private key (Below is the HEX representation of binary value)</p>

<blockquote>
  <p>7542FB6685F9FD8F37D56FAF62F0BB4563684A51539E4B26F0840DB361E0027C</p>
</blockquote>

<p>2.) Add a 0x80 byte in front of it</p>

<blockquote>
  <p>807542FB6685F9FD8F37D56FAF62F0BB4563684A51539E4B26F0840DB361E0027C</p>
</blockquote>

<p>3.) Perform SHA-256 hash on the extended key</p>

<pre><code>$ echo -n '807542FB6685F9FD8F37D56FAF62F0BB4563684A51539E4B26F0840DB361E0027C' | xxd -r -p | sha256sum -b
</code></pre>

<blockquote>
  <p>7DE4708EB23AB611371BB778FC0C8BDE80394AB2D8704D7129FB5771E2F1730D</p>
</blockquote>

<p>4.) Perform SHA-256 hash on result of SHA-256 hash</p>

<pre><code>$ echo -n '7DE4708EB23AB611371BB778FC0C8BDE80394AB2D8704D7129FB5771E2F1730D' | xxd -r -p | sha256sum -b
</code></pre>

<blockquote>
  <p>CD5C4A8E03DFBB0E3AA021C2D74A9EAA43CE4C9CB1B20FC88729A7A5834141CA</p>
</blockquote>

<p>5.) Take the first 4 bytes of the second SHA-256 hash, this is the checksum</p>

<blockquote>
  <p>CD5C4A8E</p>
</blockquote>

<p>6.) Add the 4 checksum bytes from point 5 at the end of the extended key from point 2</p>

<blockquote>
  <p>807542FB6685F9FD8F37D56FAF62F0BB4563684A51539E4B26F0840DB361E0027CCD5C4A8E</p>
</blockquote>

<p>7.) Convert the result from a byte string into Base58 to get it into the Base58Check format. This is also known as the Wallet Import Format</p>

<p>(Converted from point 6 to base58 using <a href="https://bitcointools.appspot.com" rel="noreferrer">https://bitcointools.appspot.com</a>, or using encodeBase58 from <a href="https://github.com/grondilu/bitcoin-bash-tools" rel="noreferrer">https://github.com/grondilu/bitcoin-bash-tools</a>)</p>

<blockquote>
  <p>5JhvsapkHeHjy2FiUQYwXh1d74evuMd3rGcKGnifCdFR5G8e6nH</p>
</blockquote>
